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THIS volume has been written with the hope that it will
prove a guide and be found instructive as a work of reference
to the many classes interested in the subject. The glue and
gelatine industry has made an immense advance during the
last few years. Old methods of working have given way to
new, and this changed condition of things, due to a better
scientific knowledge of the raw materials and their treatment,
the author has endeavoured to show from a practical stand-
point. Not only are the various sections replete with
information of an up-to-date character, but each step in the
manufacture is illustrated with drawings of the latest type
of machinery used. To add to the value of the work, a
section has been written dealing with the waste and residual
matters and their value when converted into fertilisers,
while another section deals exhaustively with the physical
and chemical testing of the raw and finished materials.
In conclusion, the author hopes that this work will be
found worthy of acceptance.
CHAPTER I. -HISTORICAL.
PROPERTIES OF GLUE AND GELATINE. INSTALLATION OF WORKS.
Glue-making by the ancients The sculptures of Thebes Progress
in the Elizabethan age Animal chemistry in the last century
Formation from animal tissues Glue as a nitrogenous
substance of the albuminous class Conversion compared to
that of starch into gum and sugar Constitution Glutin,
properties and composition Chondrin, properties and com-
positionSelection of site Public Health Act Power of local
authorities Ground floorage of works Railway accommodation
Electric lighting Water supply Quality of water used
Soft drainage waters from upland surfaces Natural spring or
well waters Composition Action of scale-forming salts on
boiler plates Removal of salts in the feed- water Temporary
hardness Permanent hardness Purification by the Brunn-
Lowener water-softener Value of water- softening processes
Laying out the work Ground plan, .....
CHAPTER II. GLUE.
Formation of glue Transformation of tissue Action of lime on
skins Bone glue Bones, the framework of the animal body
Mineral and organic composition Separation with acid
Collection of bones Indian and South American bones Com-
position of fresh bones Degreasing of bones Open boiling
Steaming under pressure Solvents Valves Solubility of fat
Benzene as Scotch shale spirit American or Russian petroleum
Section and plan of a degreasing plant Working of the
plant Analyses of finished fat Colour Improvements by
bleaching Limit allowed Bleaching of raw material by sul-
phurous acid Degreasing and degelatinising in one operation
Tetrachloride of carbon and the mixed vapours of benzene
and steam used as solvents Cleansing the degreased bones
Longitudinal section of mechanical cleanser Nitrogen and
phosphate of lime in coarse meal from cleanser Nitrogen not
wholly of a glue-forming nature Passage through smaller
mechanical cleanser Dust used as low-grade bone-meal or for
manurial purposes Result of trial runs Nitrogen and phos-
phate of lime in the cleansed bones, 11-20
CHAPTER III. GLUE (continued).
Work of the boiling-house Conversion of the tissues into glue
Clarification Concentration Bleaching Extraction by steam
and water Extraction by direct steam Elevation of coupled
boilers working with steam and water Section of boiling-house
working with direct steam Description of process Yield of
glue Clarifying the glue liquors Filtration Section of filters
and storage vats Concentration Evaporation in open vessels
Evaporation under reduced atmospheric pressure Vacuum
pan Yaryan evaporator Plan, front elevation, and end
elevation of the Yaryan machine Method of working Colour
of glue Bleaching by sulphurous acid gas Longitudinal
section of sulphurous acid gas generator, along with bleaching
tanks Jellying of glue liquors Hand-cutting of the jelly
Cutting by hydraulic power Hydraulic cutter before and after
cutting Cast glue Oblong tables for glue casting Drying of
jelly Conditions of drying in summer and winter Longitudinal
section of drying-house Cross -section Plans of first and ground
floors Description, ........ 21-35
CHAPTER IV. GLUE (continued).
Utilisation of wastes or residues Formation of skins Epidermis
Corium Solubility of the epidermis and corium Tanners'
wastes Blending of the wastes Classification at Gorgie Mills
Steeping in milk of lime Washing Plan of lime pits and
washers Draining and drying of the ' limed ' skins Scotch
glue Method of preparing Jellying Drying Condition of
drying Manufacture of other kinds of hide glue Section of
glue-boiling and clarifying plant Plan of ground floor Part
plan of first and second floors Method of working Residual
matter Closed boiling in France Advantages claimed
Sterilising, bleaching, and ' liming ' with bisulphite of lime
Fish glue Composition of fresh fish Treatment of fish offal
Separation of the oil and gelatinous water Clarification-
Concentration Bleaching Fish potash guano Properties of
fish glue Dissolving of glue Adhesiveness of glue Weeden-
busch's method of determining the adhesive power, . . . 36-47
CHAPTER V.- GELATINE.
Gelatine Selection of raw materials Preparation from white bones
or hide pieces Separation of organic from mineral matters by
acid treatment Steeping in dilute hydrochloric acid Washing
Bleaching Digestion Removal of the fat Clarification
with potash alum Concentration Production of high-grade
gelatine Bleaching of concentrated liquors Casting for cake
and leaf gelatine Coloration of leaf gelatine Carmine
Dissolving of aniline colours Filtering and application of the
colour Substitution of phosphoric acid for hydrochloric acid
French method of application ' Osseine ' Method of using
for gelatine The use of animal charcoal Preparation of
gelatine from the parings and cuttings of hides Use of caustic
soda and lime Bleaching Water- white leaf gelatine Sea-
weed gelatine Manufacture in the United States Production
from Laminaria Maceration Digestion with carbonate of
sodium Formation of alginic acid Washing, bleaching, and
re-dissolving in alkali Concentrating in vacuum pan Forma-
tion of the sheets Coloration like leaf gelatine Comparison
of French and English gelatines Behaviour of gelatine with
certain salts, .......... 4&-54
CHAPTER VI. SIZE AND ISINGLASS.
Size as an agglutinant Uses in various trades Size as a bye-
product Bone size Digestion Separation of fat from the
gelatinous water Evaporation and bleaching in open vat
Qualities of size Composition Size for export Composition
Preservatives Concentrated size Glue powder Isinglass
Production Commercial forms Russian isinglass Brazilian
isinglass Isinglass from Hudson's Bay, Penang, and India
Preparation of the bladders Properties of isinglass Its use as
a ' fining ' agent and also in confectionery Isinglass as an
agglutinant Diamond cement Court plaster Composition of
isinglass, .......... 55-60
CHAPTER VII. TREATMENT OF EFFLUENTS
PRODUCED IN GLUE AND GELATINE MAKING.
Effluents Stringency of public authorities Section and plan of
the Archbutt-Deeley installation Use of precipitated sludge
Marrow bones Object of treatment Sawing the ends
Steeping in salt solution Washing Digesting Separating the
fat Bleaching Composition of bleached fat Utilisation of
gelatinous water for size Drying of the partially degreased
and degelatinised bones Manufacture into buttons, etc.
Animal charcoal Carbonisation in retorts Cooling Milling
Grist of various grades Condensation of tar and ammoniacal
liquors Separation Distillation of the ammonia Formation
of sulphate of ammonia Distillation of tar Bone oil Pitch
Uses of pitch Purification of uncondensed gases Composition
of animal charcoal, ......... 61-68
CHAPTER VIII. LIQUID AND OTHER GLUES,
Liquid and other glues Waterproof glues Russian, tungstic,
chrome, portable, and frozen glues Elastic glue Cements
Jewellers' cement Cement for bottle tops Cement for leather-
Cement for attaching cloth strips to iron Universal cement
Glue for belts Glue paste for library use Glue for paper bags
Chromium glue for wood, paper, and cloth Gluing of brass
ornaments Label varnish, ....... 69-79
CHAPTER IX. -USES OF GLUE AND GELATINE.
Demand for glue and gelatine Use of glue in the manufacture of
matches Glue as an adhesive in various industries Glue as a
cheap composition in moulding mirror frames, rosettes, etc.
Glue used in the manufacture of mosaics, plaques, trays, finger-
plates, etc. Glue as a dressing for tool cuts Gelatine for
culinary and confectionery work Value of gelatine as a food
Investigation by the French Academy Liebig's opinion of
gelatine as a food Digestibility of gelatine Gelatine jelly
Use of gelatine in the arts Formation of moulds for casting
Use in photography Carbon processes of Johnson, Albert,
Swan, and others Copying of engineering drawings Con-
traction of gelatine Use of gelatine in heliography Gelatine
capsules Gelatine-coated pills Artificial ivory Artificial
leather-making Gelatine and Indian ink making Composi-
tions for printers' rollers Gelatine used in the manufacture of
artificial silk Gelatine as used in the textile trades Gelatine
as a substitute for wax, 80-88
CHAPTER X. RESIDUAL PRODUCTS FROM
GLUE AND GELATINE.
Ashes of plants Phosphates, nitrogen, and potash as plant food
Value of fertilisers used annually Skin residues Fish residues
Fish manures Bone residues Composition of degreased and
degelatinised bones Bone meal Adulterated bone meal Bone
superphosphate Phosphates of calcium Action of sulphuric
acid on tri- calcium phosphate The adjustment of sulphuric
acid used Carbonate of calcium of mechanical advantage
Composition of superphosphate Preparation in a small way
Manufacture on the large scale Superphosphate mixer Morri-
son type of mixer The horizontal mixer Gases generated
during manufacture Condensation Nature and amount of
impurities in the raw material used Absorption of acid per
cwt. of impurity Strength of sulphuric acid used Soluble and
insoluble phosphate of calcium in superphosphate Decrease of
soluble phosphate on standing Representation by equation
Dissolved bones Dissolved bone compound Peruvian guano
substitute Agricultural value of superphosphate as a manure
Experiments by Mr A. Burr Mixed or special manures-
Method of manufacture Turnip manure Potato manure
Mixings for potato manure High-class potato manure Special
manure for grass lands Special manure for cereal crops Wheat,
barley, and oat manures Pea, bean, and vetch manures Sugar-
cane manure Celery and onion manure All-round fertiliser
Manure for root crops A cheap and effective manure Recovery
of phosphate of calcium Value of the phosphate Use of pre-
cipitated phosphate as a substitute for cream of tartar in baking
Bone ash Composition Analysis of dissolved bone ash
Leather waste Used as a manure Also in the manufacture of
artificial leather, leather board, etc. , ..... 89-107
CHAPTER XI.-ANALYSES OF HAW AND
Raw bones Fat Nitrogen Benzene Condensed water Degreased
bones Refined fat Glue Gelatine Degelatinised bones
Manures Fuel Valuation of raw and finished products, . 108-132
SOME RECENT SPECIFICATIONS RELATING TO THE MANUFACTURE
OF GLUE AND GELATINE, 133-137
Table I. Testing of glue and gelatine, 138
Table II. Viscosity of glue, 139
Table III. Price, smell, viscosity, and percentage of non-gelatine in
various glues, .......... 139
Table IV. Holding power of glue joints, 140
Table V. Phosphatic strength of mineral phosphates, bone ash, and
' spent ' animal charcoal, ....... 140
Table VI. Ounce strength, percentage of ammonia, yield of sulphate
of ammonia, and weight of sulphuric acid required, . . . 141
Table VII. Supplies of nitrogen from different sources, . . . 141
Table VIII. Standard solutions 142
Table IX Factors for determining the equivalents of weighed bodies, 144
Table X. Approximate heating power of coals, . . . . 145
Table XI. Thermometric degrees, 146
Table XII. Metric system of weights and measures, . . . 147
1. Brunn-Lowener water-softener. Section, ... .7
2. Arrangement of works. Ground plan, ..... 9
3. Benzene plant. Section, . . . . . . . . 15
4. ,, ,, Plan, 15
5. Mechanical cleanser. Longitudinal section, . . . . 19
6. Coupled glue extractors. Elevation, ...... 22
7. Glue-boiling and clarifying house. Section, .... 23
8. ,, ,, ,, ,, Part plan, ground and first floors, 23
9. Yaryan evaporator. Plan, . . . . . . . 28
10. ,, ,, Front elevation, ...... 28
11. End ....... 28
12. Sulphurous acid generator. Longitudinal section, ... 29
13. Hydraulic glue cutter. Before cutting. Section, ... 31
14. ,, ,, ,, After ,,.... 32
15. Drying house. Longitudinal section, ...... 33
16. ,, First floor. Plan, 34
17. ,, ,, Ground floor, 34
18. ,, ,, Cross-section, ....... 35
19. Steeping pits and washers. Plan, ...... 39
20. Boiling and clarifying house for skins. Section, .... 41
21. ,, ,, ,, Part plan, first and
second floors, . . 42
22. ,, ,, ,, Ground floor plan, . . 42
23. Archbutt-Deeley purification plant. Section, .... 62
24. ' ,, Plan, 63
25. Soxhlet apparatus. Section, 109
(1LUE, GELATINE, AND THEIR
CHAPTER L HISTORICAL.
THE art of veneering, and consequently the use of glue,
was known to the Egyptians as early as the time of the
third Thothmes, supposed to be the Pharaoh of the Exodus.
In the sculptures of Thebes is clearly pointed out the
application of a piece of rare wood of a red colour to a
yellow plank of sycamore; and in order to show that the
yellow wood is of inferior quality, the workman is repre-
sented to have fixed his adze carelessly in a block of the
same colour while engaged in applying them together.
Near him are some of his tools, with a box or small
chest, made of inlaid and veneered wood of various hues,
and in the same part of the shop are two other men,
one of whom is employed in grinding something with a
stone on a slab, and the other in spreading glue with a
It might perhaps be conjectured that varnish was intended
to be here represented ; but the appearance of the pot on the
fire, the piece of glue with its concave fracture, and the
workman before-mentioned applying the two pieces of wood
together, satisfactorily decides the question, and attest the
use of glue by the Egyptians 3300 years ago.
2 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
Iii Pliny's time the ancients knew the value of good glue,
for he writes (as translated by Holland) :
" Great cunning there is in making strong glew,
And in the feat of joining with it too."
During the flourishing days of the Koman empire,
evidence also exists that the manufacture of glue formed one
of the industrial pursuits of the Komans ; while centuries
later, in our own Elizabethan age, glue was known as a
valuable and useful product. Shakespeare spoke in eloquent
testimony to the adhesive virtues of glue when he said :
" Go to ; have your lath glued within your sheath,
Till you know better how to handle it."
(Titus Andronicus, Act ii. scene 1.)
It is, however, due to the researches in animal chemistry
made during the last century that the industry has been
placed on a solid basis and become recognised as an important
factor in the commercial world.
Formation. When the skins and membranous tissues,
or the bones, tendons, and ligaments of animals are boiled
with water, they yield a liquor which on cooling forms a
jelly, and in a dried condition the jelly becomes a hard,
transparent, and somewhat elastic body known as glue or
gelatine, according to its colour and purity. This product
is a nitrogenous substance of the albuminous class ; it does
not exist ready formed in the tissues, but is the result of
boiling the latter in water.
How this change is effected is but imperfectly understood,
though it appears to be somewhat analogous to that of
starch into gum and sugar.
Constitution. Glue or gelatine consists of two organic
bodies, glutin and chondrin, the one or the other pre-
dominating according to the nature of the raw material
used. When prepared from skins, glutin is the main
constituent, while bone tissues yield a product containing a
large proportion of chondrin. As a cement, the former has
a greater binding power than the latter, and consequently is
of more value.
Glutin and its Properties. Glutin is a yellowish,
transparent, and inodorous body, and has the following
In parts per 100.
Hydrogen. .... 6'70
Nitrogen, .... 18'51
When immersed in cold water, glutin, while being insoluble,
loses its transparency, becomes translucent, swells, and
increases in weight by absorption of the water ; in hot
water it dissolves completely, the solution on cooling forming
a jelly. This valuable property of gelatinisation is much
reduced by prolonged or repeated heating. In a dry state,
glutin is unaffected by the atmosphere ; in solution, however,
it turns sour on standing, and in an advanced stage of decom-
position ammonia is evolved. Glutin is insoluble in alcohol
or ether, but strong acetic acid dissolves it freely ; the
solution, however, loses its jellying power, but not its adhesive
property. Hot nitric acid decomposes it into oxalic and
saccharic acids. In a solution of glutin, nitrate of silver or
chloride of gold do not precipitate the glutin, but a portion
of the metal of each salt is reduced to the metallic state ;
sulphate of copper is not reduced. Chloride of platinum
precipitates glutin from its solution in the form of brown
viscous flakes which blacken on the filter, and are afterwards
easily pulverised. This test Davy regards as a certain one
GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
for the detection of glutin in solutions which are so dilute as
to be unaffected by tannic acid.
Gallo-tannic and other tannic acids unite with glutin,
forming a compound similar in composition to that of leather,
but incapable of being used as a substitute for that material,
owing to its want of structure. The white precipitate of
tannate of glutin is insoluble in alcohol or ether, but soluble
in a warm solution of caustic potash. It forms a hard and
brittle mass on drying. Glutin in solution is not precipitated
by hydrochloric or acetic acids, alum, sulphate of iron,
ferrocyanide of potassium, or acetate of lead, but is rendered
turbid by the addition of a small quantity of chloride of
mercury. The precipitate*formed/e-dissolves on shaking, but
becomes permanent on adding excess of the reagent.
Submitted to dry distillation, glutin yields an aqueous
solution containing carbonate of ammonium, and a thick
brown oil comprising, according to Watts, aniline, picoline,
methylamine, tritylamine, pyridine, lutidine, and pyrrol,
together with certain neutral oils not yet investigated.
Chondrin and its Properties. Chondrin resembles
glutin in many respects, and was long confounded with it.
Mulder first established its separate identity. Like glutin,
it does not occur ready formed in the organisms, but is pre-
pared by boiling certain tissues with water. When dry, it
is a hard horny substance, and has the following composition:
In parts per 100.
Hydrogen, .... 676
Oxygen, . . . . . 27'67
On immersion in water, in which it is insoluble, chondrin
increases in weight by absorption. It is also insoluble in
alcohol and ether, but in hot water it dissolves completely,
the solution on cooling forming a stiff jelly. Watts states
that nearly all the acids, even organic, precipitate chondrin
from its aqueous solution. The precipitate formed by
phosphoric, hydrochloric, nitric, or sulphuric acids, easily
dissolves when excess of the acid is used, while that formed
by sulphurous, pyrophosphoric, hydrofluoric, carbonic,
arsenic, tartaric, citric, oxalic, lactic, or succinic acid remains
permanent in presence of excess.
Chondrin, unlike glutin, is precipitated from aqueous
solution by alum, sulphate of alumina, acetate and subacetate
of lead, and sulphate of iron, the precipitate being soluble in
excess of the reagent used. When submitted to dry distilla-
tion it yields the same products as glutin.
Chlorine forms a precipitate in a solution of chondrin
resembling in composition that produced with glutin; no
similar product is obtained by substituting bromine or iodine
Selection of Site. The selection of a site for the
factory is a matter which requires every consideration by the
intending manufacturer. In the first place, the business
of glue or gelatine manufacturing is an offensive business
within the meaning of section 32, sub-section 1, of the /
Public Health Act, and sanction is thus required from the
local authority before such a business can be carried on ;
and this sanction is withheld if it is considered that the
establishment of such a works would affect the amenity of the
surrounding district and the health of the resident population.
Undoubtedly a smell, sometimes of a very nauseous character,
does arise from the raw materials before and during treat-
ment, but, however unpleasant it may be, no evidence exists
to prove that it is unhealthy, or that it tends to increase
the death-rate of the contiguous district. In face of the
prejudice existing against a business of this nature, the
6 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS
intending manufacturer would be well advised if he selected
a site outside the boundaries of a town, so that any smell
would not give cause for complaint. In the erection of the
works an important matter is the ground floorage, all of which
should be concreted, and connected with a suitable drainage,
so that it may be kept clean by washing.
Railway Accommodation. Kail way access to the
works by means of a siding is a necessity, and a canal
communication also would be of service as a cheap means
of receiving and dispatching raw and finished materials.
Lighting. As gas, even if obtainable, would not be a
safe illuminant in certain departments of the works for
instance, the benzene house an installation for electric
lighting is laid down in all works using the solvent process,
the current being generated from machinery driven by steam,
or, if available, water-power.
Water Supply. Another very important point is the
water supply. Water is used not only for the raising of
steam, but also for manufacturing purposes, and to fulfil
both requirements it is essential that it should be soft or
only moderately hard, of good colour, and free from any
decomposing animal matter. Further, the water should have
no acid reaction or contain any iron likely to injure the
quality of certain classes of glue. The waters having these
qualities are the drainage waters from upland surfaces.
They are generally very soft, owing to the fact that their
mere surface contact with the soil does not lead to the
extraction of any considerable quantities of the salts present
in the latter, and that any organic contamination there may
be is of vegetable and not animal origin, as evidenced by
the small proportion of nitrogen in comparison with the
carbon usually found in such waters.
If surface waters are not available, and the supply is
dependent on natural spring or well waters, the latter,
although suitable for manufacturing purposes, would require
a softening treatment before being used for steam-raising,
owing to the scale-forming salts they invariably contain.
These salts, composed of carbonate and sulphate of calcium
with carbonate of magnesium, crystallise out when the water
becomes saturated in the boiler, forming, especially when
sulphate of calcium is present to any extent, a hard incrusta-
tion on the boiler plates, which not only causes a considerable
loss of heat, but also renders the plates liable to be damaged
The removal of these salts in the feed water is a necessary
action if the boiler is to be
preserved and a saving of fuel
effected, and is carried out by
a method of precipitation, as
adopted in the several water-
softening processes now in use,
the reagents employed being
lime and soda-ash, the former
removing the temporary hard-
ness of the water due to dis-
solved ''carbonates of calcium
and magnesium, while the latter
decomposes the sulphate of
calcium constituting the per-
Water Softening. In fig.
1 is shown a section of the
Brunn - Lowener continuous
water-softener, as given in a
very interesting report on the purification of feed waters by
Mr C. E. Stromeyer, the chief engineer of the Manchester
Steam Users' Association. The process is carried out by
dissolving the lime and soda-ash by the aid of a steam jet in
FIG. 1. Brunn-Lowener water
8 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
a semi-cylindrical tank A, fitted with a blade B, which every
now and then stirs up the milky mixture. The water supply
from the pipe C is run into a measuring tip D, consisting of
two triangular troughs ; when one is full it tips over and
allows the other to fill ; while tipping, it moves the stirrer,
and also momentarily opens a little valve at the bottom of
the tank A, which allows a definite quantity of the chemicals
to be discharged. This and the water from the tip D falls
into the mixer E, and from there they flow into the settling
tower F, the sediment remaining at the bottom ; the nearly
clear water passes through the filter G-, and is discharged to
a feed-tank through the pipe H.
The proportions of lime and soda-ash used vary according
to the hardness of the water treated, some requiring only
1J Ibs. lime and \ Ib. soda-ash for every 1000 gallons to be
Eoughly speaking, the cost of a plant for treating 1000
gallons of hard water per hour would be from 150 to 200 ;
and as 750 gallons per hour is as much as one 8-feet
Lancashire boiler can evaporate, Mr Stromeyer considers
that it is cheaper to adopt a water-softening process than to
lay down a spare boiler if only one is in use ; and even if
there are six boilers, the advantage would still be with the
softening plant, on account of the less cost of chemicals,
which could then be used and the saving in the cost of
In laying out the works, the following ground plan (fig. 2)
may be of interest. The references to the plan are given
a Works' siding. / Mechanical cleanser.
1) Storage for fresh bones. g Acid-steeping vats.
c Crusher. h hhh Lime pits for skins.
d Conveyor. i i i Skin washers.
e Benzene house. j Skin-boiling house.
10 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
k Bone-boiling house. q q Tanks for effluents.
I Jellying and drying house. rrr r Steam boilers.
m Storage for boiled bones. s Chimney.
n Warehouse. t Office and laboratory.
o Manure house. u Canal wharf.
pp Marrow bones.
CHAPTER II. GLUE.
Formation. When subjected to the action of heat and
water, the skins and tissues of nearly every animal yield a
certain proportion of glutinous matter, which on desiccation
forms a hard, glassy-looking substance known as glue.
The treatment of skins with milk of lime not only dissolves
the blood and epidermis, but in some way predisposes the
tissue to be converted into gelatine, and this action is
enhanced by the subsequent drying of the 'limed' skins.
This change, however, does not result in the formation of
gelatine, but only assists, the transformation into the latter
body being effected by the after-process of boiling.
With bones the membranous tissue forming the ossein is
identical in composition with gelatine, but, unlike the latter,
is totally insoluble in water, and it is only by the action of
steam or hot water that the conversion is effected into a
soluble gelatine. Solutions of glutinous matter have the
valuable property of jellying when cooled, and this power
of gelatinisation depends, according to the late Dr Gregory,
Professor of Chemistry, Edinburgh University, on the
presence of small proportions of phosphate of lime, for when
gelatine is long boiled with water alone, or with a little
alkali, phosphate of lime is deposited, and the solution no
longer forms a jelly on cooling.
GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
Bone Glue. The glues of commerce are classified as
bone or skin glues, according to the nature of the raw
materials used in their preparation, and their methods of
manufacture will now be described.
Bones constitute the framework supporting the softer
portions of the animal body, and are rendered stiff and rigid
by earthy salts, composed mainly of phosphates of lime and
magnesia and carbonate of lime. The proportions of earthy
and organic matter vary with the kind of bone and the age
of the animal, the bones of the adult containing more earthy
salts than those of a young animal. On the other hand, the
organic matter, though less in quantity in the old, has
practically the same composition as that of the young
animal, as is seen from the following analysis by Fremy :
Ox (old), .
Calf, . . .
In parts per 100.
The organic matter may be separated from the earthy
salts by steeping the bones in a dilute solution of hydro-
chloric acid, which dissolves out the phosphates of calcium
and magnesium, along with carbonate of calcium, leaving a
skeleton which retains the size and form of the original
bone. This substance is semi-transparent, soft, and flexible,
and when dried resembles horn. On boiling in water it is
converted into gelatine, with the exception of a few fibres
which are insoluble and may be separated by filtration.
Degreasing of the Bones. Bones as used in the works
are delivered in a fresh condition, or as marine store bones
which have generally been used for making soups. Naturally
the former yield more fat and glue than the latter. Taking
an average, fresh bones comprising the heads, ribs, shoulder-
blades, etc., yield 12 to 13 per cent, fat, while from the large
thigh bones, known as 'marrows/ 17 to 18 per cent, is
Owing to their having been previously steamed, Indian
and South American bones are poor in fatty and gelatinous
matters, and are mainly used in this country for manurial
The following analyses, by the author, indicate the
composition of fresh bones :
In parts per 100.
Moisture, .... 1T55 12'88
Fat, . . . 12-69 1242
Organic matter other than
fat, .... 21-64 21-29
Phosphates of calcium and
magnesium, . . .' 47'83 48'66
Carbonate of calcium, . 3'14 2*74
Alkaline salts, . . . 2'67 172
Silica, etc., ... "48 -29
Of these constituents, the fat is used in the manufacture
of soap, glycerine, and other products ; the organic matter
other than fat furnishes glue and gelatine, while the
phosphates form the basis of artificial manures.
The first stage in the treatment of bones is the extraction
of the fat, the yield of which varies according to the method
employed. The degreasing can be carried out (1) by open
boiling of the bones in a wooden vat provided with a steam
coil ; (2) by digestion under steam at 40 Ibs. pressure ; and
(3) by solvents. The yield of fat by the first process is low,
averaging only 5 per cent. ; by the second, this amount is
14 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
increased to 7J per cent., with the removal of a large portion
of the gelatinous matter ; while by the adoption of the
third method, practically the whole of the fat is obtained,
leaving the tissues unimpaired for subsequent conversion
On a working of 100 tons fresh bones the money value of
the fat recovered, based on a value of 25 per ton, would be
(1) Open boiling, . . . 125
(2) Steaming under pressure, . 187, 10s.
(3) Solvents, . 312, 10s.
As is well known to chemists, animal and vegetable fats
are soluble in ether, alcohol, benzene, petroleum, bisulphide
of carbon, and other solvents, and on this property is based
the system of extraction which is now superseding the old
methods of open boiling or steaming (under pressure) the
fresh bones. Of these agents ether and alcohol are used
mainly for laboratory determinations of fat, while bisulphide
of carbon, though an excellent solvent, is found unsuitable
in working, from its low volatility. In practice the best
solvents are found to be Scotch shale spirit and American
or Eussian petroleum, with boiling points at or about
212 F. and distilling completely over between 270 F.
and 280 F.
In fig. 3 is seen a section, and in fig. 4 a plan, of a
modern installation for the degreasing of bones. The main
building contains six extractors, each of five tons capacity,
and their working is so arranged that while half their
number are under the action of the solvent, the other
half are being emptied of the degreased bones preparatory
On delivery to the works, the bones are shovelled on to a
sorting table A, and the hoofs, horns, and any pieces of iron,
16 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
wood, etc., removed. From thence they pass through the
mill B, which slightly cracks them, to the elevator C, and are
discharged on the upper floor D of the extracting house.
Each of the extractors E is provided with, charging, F, and
discharging, H, manholes, and has a false bottom G, under
which rest the dry and wet steam coils supplied from the
pipes J in connection with the main steam pipe. At the
top of each extractor is fixed the outlet pipe K for conveying
the solvent and steam vapours to the condensers XXX,
which are placed at an elevation outside the main building.
After condensation, the solvent and water flow into the
receiver Y, where the former, from its lighter gravity,
separates from the water and is run into the storage tank Z,
from whence the supply to each extractor is brought through
the pipe I. All the pipes are supplied with the necessary
valves and cocks.
On the extractors receiving their full complement of
bones, the charging manholes are securely fastened and the
first run of solvent is made to a depth of 2 feet, as measured
in the gauge-glass fixed to each extractor, and heat gradually
applied through the dry steam coils. As the operation
proceeds, the solvent is gradually distilled over, carrying with
it the moisture mechanically held by the bones, and at a
point when it becomes but barely visible in the glass, the
steam through the dry coils is shut off, the discharge valves
L L L opened, and the first charge of extracted fat is run
through the pipe M to the montejus or distiller. This action
is repeated with a second, third, and fourth run of solvent
from the storage tank, the fat left at the end of each action
being run to the mont-jus as before. With the finish of the
fourth charge of solvent the bones are found to be practically
deprived of their fat. They still, however, retain a portion
of the solvent, and to recover this, the wet steam valve is
opened and high-pressure steam (70 to 80 Ibs.) blown through
the mass of bones until the faintest film of solvent only is
seen separating from the condensed water running into the
The operation, which has taken from eleven to twelve hours,
is finished with the closing of all valves and the removal of
the manhole doors to facilitate the escaping steam, and to
dry the bones, which are then raked out and conveyed by a
railway to the cleanser, and from thence to the glue-boiling
house. The degreased bones are in a dry condition, free
from smell, and retain on an average only '2 per cent, of
fat on being withdrawn from the extractors.
In the meantime, the crude fat is receiving attention in
the mont-jus. As it leaves the extractors, it retains a portion
of the solvent along with dirt and mineral matter, and it is
the object of the second distillation to recover this solvent,
the other impurities being removed by a subsequent washing
which the fat receives.
The mont-jus T is a still heated by the steam pipe V, and
is provided with an outlet pipe 0, through which are
conveyed the solvent vapours to the main pipe of the con-
densers. On the mass being brought to the boil, the solvent
vapours pass freely over and the heat is continued for about
two hours, at the end of which time the fat will retain only a
faint smell of the solvent, while the film at the receiver will
be but barely visible. These results being attained, the
main valve is closed and hot water run in through the pipe
Q from the cistern P, heated by a connection from the main
steam pipe. As the water flows in the fat is floated through
the pipe R, the valve of which has been opened, to the
washer S, where it undergoes a boiling with water for three
hours, the aim being to deposit the dirt and mineral matter
and leave a clean fat, which is floated off by means of hot
water, the stream of fat being distributed by pipes into a
number of casks conveniently placed for filling.
18 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
Analyses of Finished Fat. The following analyses, by
the author, represent the composition of the finished fat :
In parts per 100.
Moisture, . . 1-181 732 1406
Naphtha, . . '031 "008 '005
Ash (mineral matter), -169 '121 '287
Organic matter other
than fat, '072 -093 136
Fat, . . . 98-547 99'046 98166
100-000 100-000 100-000
Fat extracted by solvents is darker in colour than that
produced by boiling or steaming the bones. The colour,
however, can be brought up to a good white by bleaching.
It is bought on a basis of 98 per cent., a limit of 2 per cent,
being allowed for moisture and other impurities. In order to
improve the colour of the fatty and gelatinous matter of the
bone, some manufacturers, prior to the benzene treatment,
blench the raw material by immersion in a very dilute
solution of sulphurous acid. As presently carried out,
the degreasing by solvents and the subsequent degelatinisa-
tion of the bones after cleansing, form three operations
which are costly to the manufacturer, from the frequent
handling of the material and the heavy consumption of
steam. To reduce this cost attempts have been made to
combine the degreasing and degelatinising of the bones in
one operation, and thus dispense with the cleansing process.
To this end, tetrachloride of carbon, and also the mixed
vapours of benzene and steam acting in a battery of extractors
working together, have been suggested. Unfortunately, while
the extraction of fat is up to the standard, the resulting
gelatinous liquor fails to yield a clear and bright glue.
The process of cleansing has for its object the removal of
loosely adhering dirt and fleshy matter, and is carried out in a
large cylindrical drum A (fig. 5), measuring 14 feet in length
by 7 feet in diameter, horizontally working on a central
shaft. The drum is open at both ends, and covered with
a stout wire gauze. At the charging end B the degreased
bones are fed through a hopper C, and as the drum slowly
revolves they undergo a polishing action by friction, the
detached mineral and organic matter falling through the
meshes of the wire gauze into a chamber D below. From
FIG. 5. Mechanical cleanser. Longitudinal section.
the discharging end E the cleansed bones are conveyed to the
acid steeping vats for gelatine making, or to the glue house.
As is seen from the following analyses by the author,
Phosphate of lime,
the coarse meal passing through the meshes of the cleanser
contains a high percentage of nitrogen, which, however, is not
wholly derived from the bone itself, but partly has its
origin in the hair of skins connected to the bone, or passing
GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
in a loose state into the extractor. In the former condition
only is the nitrogen of a glue-forming nature, and to recover
it the coarse meal is passed through a smaller revolving
cleanser, covered with a 30-mesh wire. Here fully half the
weight is separated, and as it leaves the discharging end of
the cleanser is bagged and passed on to the glue house for
The dust or flour falling through the netting is sold as a
low-grade bone meal, or used in the mixings of the manure
The following yields are taken from the returns of several
runnings made with raw bones :
t. c. qrs. Ibs.
8 7 21
8 11 3 17
t. c. qrs. Ibs.
t. c. qrs. Ibs.
4 18 3 12
5 1 2 26
t. c. qrs. Ibs.
4 11 3 4
4 17 24
c. qrs. Ibs.
6 1 4
When in a condition ready for glue-making the cleansed
bones contain 5 to 6 per cent, of glue-forming nitrogen and
58 to 62 per cent, of phosphate of lime.
CHAPTER III. GLUE (continued).
As previously remarked, glue does not exist ready formed
in nature, but is the product of heat on nitrogenous animal
tissues, and this work, as carried on in the boiling house,
requires the exercise of much knowledge and skill on the
part of those engaged in it. The operations of the boiling
house may be divided into (a) Conversion of the tissues into
a glue liquor by steam and water ; (b) clarification ; (c) con-
centration ; (d) bleaching.
With steam and water alternately playing on the bones,
or by the action of direct steam, the extraction is made in
large boilers, built of steel plates f in. thick and holding
from three to five tons according to the method used. By the
adoption of the first, the boilers A A are worked in couples
as seen in elevation, fig. 6. The glue liquors are, however,
bulky, and low in strength, which renders them troublesome
in clarification and costly in concentration. For these
reasons many manufacturers prefer the second or direct
steam method as a more economical process of extraction.
In fig. 7 is represented a section of a boiling house working
with direct steam and illustrating the arrangement of boilers,
clarifiers, etc , the ground and first floors being shown in
part in the plan, fig. 8. Each boiler A is fitted with a false
bottom B and provided witli charging and discharging man-
GLUE : GELATINE, AND THEIR ALLIED PRODUCTS.
holes CD. A steam gauge E is also attached to regulate the
pressure of steam, which enters the extractor by the pipe F
in connection with the main steam pipe G. The cleansed
bones are raised to the first floor of the boiling house by an
elevator, and after charging each boiler, the steam is turned
on and kept at a pressure of 15 Ibs. for two hours, and then
FIG. 6. Coupled glue extractors. Elevation.
reduced to 5 Ibs. This lowering of the pressure enables the
glue formed within the bone to come to the surface, and is
washed down by a spray of water from a coil fixed in the
dome of the boiler. The action is repeated until a sample,
on being tested by the glue meter, indicates a strength of
about 20 per cent, dry glue. When this density is attained
a first discharge is made to the clarifiers placed on the first
FIG. 7. Glue boiling and clarifying house. Section.
FIG. 8. Glue boiling and clarifying house. Part of plan.
Ground and first floor.
24 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS,
floor, as shown in section and plan, by opening the valve of
each outlet pipe H and blowing the liquors to the vats I.
Taking the average, degreased and cleansed bones are
capable of yielding over two-fifths of their weight of glue,
and in the first run to the clarifiers the extraction will be
from 65 to 70 per cent, of this quantity. The remainder,
with the exception of about 4 per cent, which is practically
irrecoverable, is obtained by a second steaming of the bones,
the liquors being forced up to the clarifiers by steam
It will be readily understood that these liquors are far
from being pure, and for the production of high-grade glues
they require to undergo a process of clarification.
Although many ingredients have been proposed for
clarifying glue liquors, as oxalic acid, phosphate of soda,
basic acetate of lead, blood, etc., nothing as yet suggested
fulfils the purpose to better advantage than potash alum,
when used in the proportion half per cent, of the weight
of dry glue present in the liquors. In the application, a
bucketful of the liquor, which should have a temperature of
about 80 C., is drawn from each vat, the necessary quantity
of alum stirred in, and the contents thoroughly mixed in the
mass, the heat at the same time being raised to 100 C. by
means of a steam pipe M. After boiling for ten minutes
the steam is turned off and the liquor allowed to settle,
during which the heavier mineral and organic impurities fall
to the bottom, while the lighter form a coagulated scum on
the surface. These impurities are separated by filtration;
for this purpose the valve J of each vat is opened and the
liquors allowed to flow to the filters made of fine wire gauze
or medium woven calico fixed on to a wooden framework.
The two filters K K, one of which is shown in section, fig. 7,
are placed over the receivers or storage vats L L, into which
flow the filtered liquors, the heat being maintained by the
GLUE CONTINUED. 25
steam pipe N. Clarified glue solutions are never jellied
below a strength of 32 per cent, dry glue in winter and 35
per cent, in summer; and to remove the excess of water
necessary to obtain the density required, they undergo a
process of concentration by passing them through an
The utility of evaporating apparatus in connection with
modern manufacturing processes is now widely recognised,
and this recognition is fully shared by those engaged in the
glue and gelatine industry.
As is well known, gelatinous solutions undergoing
concentration are very susceptible to change by prolonged
boiling at the normal atmospheric pressure, and consequently
the evaporation of these liquors in open vessels at a
temperature of 100 C. always yield a dark-coloured and
To remedy this, advantage has been taken of the fact that
the boiling point of a liquid depends upon the atmospheric
pressure exerted on its surface, and if this pressure is
reduced the boiling point is lowered accordingly.
For instance, at the sea-level the boiling point of water is
100 C. under an atmospheric pressure of 15 Ibs. on every
square inch of water surface. If, however, this pressure is
reduced by mechanical means to, say, 9 Ibs., the boiling point
is lowered to 857 C., while at 3 Ibs. pressure it falls to 60 C.
On this principle is based the vacuum pan, first introduced
by Howard, and its more modern application is seen in the
well-known Yaryan type of evaporator invented by Mr
Homer T. Yaryan of Toledo, Ohio, U.S.A. The vacuum pan
is of a globular form, and built of wrought iron or steel
plates. It is heated by a steam jacket encircling the lower
part of the pan, and by a coil of piping immersed in the
liquid. At the top is fixed the dome fitted with baffle-plates,
to which is connected the condenser and vacuum pump. The
26 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
pan is further provided with a steam and also with a vacuum
gauge, and the concentrated liquors are discharged through
an outlet valve fixed to the bottom.
The vacuum pan cannot be considered an economical
method of evaporating a liquor, for, although a large amount
of work may be performed per square foot of heating surface,
yet for every pound of water evaporated out of the liquid
under treatment, an equal weight of steam or more, accord-
ing to the initial temperature of the liquor is produced
having the latent heat of the original steam, which, though
capable of doing useful work, passes directly to the condenser,
there to be uselessly absorbed by the condensing water.
Now if this steam were conducted to the jacket and coil
of a second pan working under slight vacuum it would
generate nearly its own weight of steam at a lower pressure
and temperature, and so evaporate the water from the second
pan. This steam would be available for a third pan, and the
service may be continued until the original heat of the steam
is wasted by radiation and other causes.
This is the principle of the double and multiple effects as
used in the Yaryan type of evaporator, and its economical
advantage is noticed in the fact that for every pound of coal
consumed in the boiler fire to generate steam for the jacket
and coil of the vacuum pan only 8 Ibs. of water are evaporated
from a glue liquor, while in the double effect 16 Ibs. are
evaporated for the same consumption of fuel, and 23J Ibs. in
the triple effect.
A further advantage claimed by the Yaryan is the limited
time the glue liquors are under heat, only three minutes
elapsing from the time of entering the machine to their
delivery at a strength ready for jellying. This short duration
of heat exposure is an important consideration in the after-
production of a good cake of glue.
Through the courtesy of the makers, Messrs The Mirrlees
GLUE CONTINUED. 27
Watson Company, Ltd., engineers and founders, Glasgow,
the author is enabled to give a complete drawing of the
Yaryan, which is now extensively used in the concentration
of glue liquors. In figs. 9, 10, and 11 are shown the plan,
front elevation and end elevation respectively, of the
The Yaryan consists of two or more horizontally placed*
cylinders forming the double, triple, or multiple effect as
required. Each cylinder contains a series of tubes heated
by steam, the first one only by original steam. The tubes
are coupled at the ends, and are divided into sections termed
coils. Thus a continuous passage exists from end to end.
As the glue liquor is pumped in at the inlet in a thin stream
it undergoes the initial stage of evaporation, the liquid and
vapour travelling from section to section, and so come into
contact with the whole heating surface of the tubes. Moving
at a high velocity, owing to the steam generated, the liquor
and vapour on issuing from the last tube pass by a pipe to
the separator, from which the steam escapes by a connection
to the * safe ' or ' catch-all.'
This vessel encloses a number of tubes through which the
steam travels, then impinges on the end of the vessel, and
there deposits any liquid it may carry. From the separator
the liquor is discharged by a branch pipe to the second
Yaryan or cylinder, which is heated by the steam from the
' safe.' In a triple effect (as shown by dotted lines in the
drawing) or a multiple effect, the steam generated in the
second Yaryan is used for heating the third, in the manner
described above, and this in turn supplies the steam to the
fourth effect, and so on ; from the last separator in the series,
it is condensed by passing through a condenser. As will be
noticed in the drawing, each Yaryan is worked under a
vacuum, the object being to secure the low temperature only
obtainable by this means.
GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
The apparatus, the double effect of which is most suitable
for evaporating glue liquors (owing
to the lower steam pressure at which
it is worked), is easy of installation,
and is readily adaptable to the exi-
gencies of space in a glue house, for
the cylinders can be arranged one
above another, or horizontally side by
side without affecting their efficiency.
Colour being an important matter in
the selling of glue or gelatine, the
concentrated liquors now undergo a
process of bleaching by means of sul-
phurous acid. Some manufacturers
bleach during the clarification process,
but it is preferable to do so after
concentration. Sulphurous acid is
applied either as a solution or in the
gaseous form ; the latter, however, is
more economical for use and can be
better regulated in the obtaining of
any desired shade of colour.
Fig. 12 represents a longitudinal
section of the sulphurous acid genera-
tor, along with the tanks in which
the bleaching of the liquors delivered
by the discharge pump of the Yaryan
apparatus is effected. A is the air-
compressing engine throwing a current
of air into the iron cylinder B, in
which is placed a tray containing
ignited sulphur. This substance burns
to sulphurous acid by means of the
oxygen of the air blown in, and the gas is then washed by
30 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
forcing it through the lead-lined washer C. After bubbling
through the water, it is conveyed by the pipe D to the
tanks EE, and delivered to the liquors by means of a coil
of perforated piping F F, arranged in a manner similar to
the shape of a gridiron. Each tank is also provided with
a dry steam coil to prevent any cooling action during the
bleaching. The progress of the bleaching is readily ascer-
tained by withdrawing a sample, and setting it aside for a
few minutes to cool ; when the formed jelly corresponds in
colour to the shade required, the action is stopped.
The concentrated and bleached liquors are now ready for
jellying, and to effect the congelation they are run into
galvanised sheet-iron troughs, having a length of 2 feet, a
width of 6 inches, and a depth of 5 inches, and allowed to
stand for twelve hours in a cool and dry place. Having
become a firm jelly, the tremulous mass is removed, either by
cutting round the edges with a knife and then overturning
the trough, or by slightly warming the latter in hot water,
which by softening the outer portion of the jelly, easily
allows of its removal on turning the trough over.
Although mechanical means have been devised, of which
may be mentioned the Schneible machine, to cut the blocks
into cakes of the size and thickness desired, they have but a
very limited use in this country, as manufacturers generally
prefer to use the * wire knife,' which gives to the cakes the
wavy appearance desired in cut glue, and which is not
obtained by a glue-slicing machine. In cutting in this way,
the jelly block is placed in a wooden box open to the back
in several slits or divisions, of a size corresponding to the
thickness which the cakes of glue are required to have. It
is then cut into slices by passing a brass wire stretched in a
frame like that of a bow-saw along the slits. On removal of
the sides of the box, the sliced block of jelly is cut with a
wet knife into divisions representing the size of the cakes
GLUE CONTIN UED.
desired. Cutting by wire is effected in some Continental
glue works by a machine, and an ingenious contrivance used
for this purpose is represented in section in fig. 13. A is a
platen which is raised by the ram B, worked by water
power. The platen forms the bottom of a chamber C, D D
being the ends, while the top E is a hinged framework of
wood, on which are stretched the cutting wires F. In the
chamber, and resting on the platen, is placed the glue block,
FIG. 13. Hydraulic glue cutter. Before cutting. Section.
and on raising the platen by hydraulic pressure, it is forced
through the wires, which slice it into cakes ready for drying.
Fig. 14 illustrates the position of the platen and glue block
The larger proportion of glue brought into the market]
is in the form of cast glue. In producing it, the cooling!
troughs are dispensed with, the liquors being jellied in sheets
on glass slabs fixed on long rows of oblong tables A, figs. 1 7
and 18. Between the bottom of the glass and the top of the
GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
table a constant flow of cold water is allowed to run for the
purpose of better congealing the glue solutions which cover
the slabs to a depth of from one quarter to one-half inch,
according to the thickness desired.
At the Gorgie Works of Messrs Cox, Limited, Edinburgh,
the glass slabs are fed from small round cylinders, which
carry the glutinous liquors by means of an overhead railway
suspended from the ceiling. When stiffened to a proper
FIG. 14. Hydraulic glue cutter. After cutting. Section.
consistency, the jellied sheets are cut with a wet knife into
small cakes of the size required.
The drying of the jelly is a very important stage in the
manufacture of a cake of glue, and although, in the modern
method of desiccation, the difficulties which attended open-
air drying, and which limited the work to temperate and
equable weather, are largely surmounted, yet the process
requires very great care if a good and saleable product is to
be obtained. Glue in a jellied condition is not capable of
withstanding a higher temperature than- 2'5 C. ; above this
it softens and becomes unshapely, so much so as to run
through the nets, or get attached to the strings, and surround
them, so as not to be separable without the use of hot water.
In hot weather, therefore, the air is cooled by passage
through a refrigerator before coining into contact with the
congealed cakes. On the other hand, the air in winter is
too low in temperature to be effective as a drying agent,
and in addition is generally so humid that the moisture on
condensation would occasion a mouldiness on the surfaces of
the cakes. For winter work, then, it becomes necessary to
reverse the conditions of summer drying, by warming instead
of cooling the air, and this is effected by passing it between a
FIG. 15. Drying house. Longitudinal section.
series of 6-inch pipes, heated by waste steam, before entering
the drying chambers.
Fig. 15 represents a longitudinal section, fig. 18 a cross-
section, and figs. 16 and 17 the first and ground floors
respectively, of a modern drying-house. Whether the glue
liquors are jellied in troughs or cast on glass slabs, the con-
gealing is carried out on the ground floor, which in summer
is kept cool by a refrigerator (not shown in the drawings).
Here also are placed the cutting tables B B, or the cutting
machine, if one is used, as seen in figs. 13 and 14, and
the engine C, driving the exhaust fans above. On this floor
the cut or cast cakes of jelly are lifted on to frames, 4 feet
GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
in length by 2 feet in width> formed of netting stretched on
a wooden framework, and these are built up on a bogie
forming a rack D, which enables the cakes to be equally
FIG. 16. Drying house. First floor plan.
exposed to the action of the air. The rack is raised by the
hoist E to the first or drying floor.
As will be noticed in the plan, fig. 16, and the section,
FIG. 17. Drying house. Ground floor plan.
fig. 18, this floor is partitioned into three main divisions
running the length of the building, the two outer being
further subdivided into chambers or tunnels K K K K.
M M M M are the steam pipes heating (in winter) the air
before its passage through the chambers, and L L the fans,
actuated from the countershaft N. Access is gained to the
chambers through the sliding doors 1 1 1 1.
In the central division F the glue racks are received from
the hoist E and conveyed over the tramway G- to the turn-
table H, passing thence to the chambers on the right or left
by the turntables J J J J. When the chambers are filled,
the doors are closed and the fans set in motion. At the\
maximum speed, the strength of the current may be judged I
from the fact that 20,000 cubic feet of air are drawn through I
each chamber every minute, and in passing over the frames, f
FIG. 18. Drying house. Cross-section.
absorbs the water of the jellied cakes without unduly pre-
venting their contraction to the proper size.
The temperature of the current is noted by Centigrade
thermometers conveniently placed in each chamber, while
its humidity is recorded by dry- and wet-bulb hygrometers.
The drying, which occupies from four to five days, is carried
on continuously, and finally yields a hard and solid product
retaining from 10 to 13 per cent, moisture. When this end
is attained, the racks are removed from the chambers, and
the dried cakes conveyed to the warehouse n (fig. 2) to be
sorted and then carefully packed in bags, barrels, or tin-lined
CHAPTEK IV. GLUE (continued).
Skin Glue. Nothing in the industrial world is more
indicative of progress than the utilisation of wastes or
residues from manufacturing operations, and an evidence of
this progress is seen in the establishment of a great industry
largely dependent for its raw material on the wastes produced
in the treatment of ox, calf, sheep, and other skins.
The skins of animals consist of two layers : (1) the outer,
in which the hairs are developed, certain sudoriferous and
sebaceous glands, and is known as the epidermis] (2) the
inner layer, called the corium. The epidermis, though
soluble by prolonged immersion in boiling water under
pressure, does not yield a gelatinisable liquor ; on the other
hand, the fibrous connective tissue, which forms nearly 95
per cent, of the corium, is wholly soluble in boiling water,
and yields a liquor having the property of gelatinisation on
cooling. By treating the corium with any of the vegetable
tannins, as in the process of tanning, the well-known sub-
stance leather is produced, this product being chemically a
tannate of gelatine.
The raw materials of the glue-maker form a surprisingly
heterogeneous collection. Such things as the clippings of
hides, ear and tail pieces of ox, calf, and sheep, rabbit skins,
scraps of parchment, and many other apparently worthless
things, all contribute their quota.
GLUE CONTINUED. 37
The hides as brought into the market are classified into
oxen, ranging in weight from 53 to 93 Ibs., cows, bulls, cut
bulls, heavy cuts, medium cuts, light cuts, salted Irish hides
and kips, horse, etc. ; while the lighter skins are arranged as
calf, damaged calf, kips, wool, Scotch lamb, pelts, etc.
Previous to the tanning process with the extracts of
valonia, myrabolans, divi-divi, gambier, quebracho wood,
and other barks, the hides and skins are limed and unhaired
in the usual way, and then subjected to a clipping process
which removes the tail, head and ear pieces, parts which,
though useless for leather-making, form valuable raw material
for the glue-maker. A fine quality of glue is also produced
from the residues in the manufacture of kid gloves. The
raw skins are prepared by immersion in milk of lime for
from two to three weeks. The skins are constantly turned
and shifted about by workmen armed with long iron tongs,
and when taken out of the pits, it is found that the lime has
loosened the cuticle of the skins, thus rendering the removal
of the hair a more easy matter. From the lime pits the
skins are taken to the unhairing room, where they are
stretched on a wooden block and scraped with a blunt two-
handled knife. They are now taken in hand by the ' flesher,'
who cuts off the tail, the head piece, and the portions of
adipose matter which may still adhere to the skins. The
waste pieces are in great demand by the glue-maker, the
hair being used for mortar and for felt-making.
The range of raw materials used by the glue-maker would
be much extended if leather waste could be used in the
manufacture. Leather is a tannate of gelatine, and the
attempts at separating the two constituents so as to render
the gelatine available for glue-making has not met with any
practical success. According to Mulder, it appears that
several definite and permanent combinations of gelatine with
tannic acid are capable of being formed. On commingling
38 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
the pure solutions of these bodies, a neutral combination
containing one equivalent of gelatine, one of tannic acid, and
two of water, is formed. From the investigations of Davy,
the compound of gelatine with oak-tannin consists of
In parts per 100.
Tannic acid, 46
When leather is acted upon by a dilute solution of
ammonia, much of the tannic acid is extracted, and there is
left a gelatiniform, mucilaginous, swollen mass, which, with
the aid of heat, dissolves like gelatine ; but it is found that
the solvent employed for removing the tannic acid has also
taken up a certain quantity of gelatine ; if the mass in
question be digested with water, a little of the gelatine
dissolves out, while the remainder is converted into a com-
bination of gelatine and tannin which is precipitated with
In the manufacture of high-class glues, much discretion
is required in blending the various waste products from the
tannery, and experience has shown that a mixture of hide,
ear, and face clippings from the ox and calf yields the best
glue. At the Gorgie Mills of Messrs Cox, Edinburgh, the
raw material is classified into three great divisions for the
purpose of manufacture, viz. : (1) sheep pieces and fleshings ;
(2) ox fleshings and trimmings ; (3) ox hides and pieces.
The first stage the raw material, or 'stock/ as it is
technically termed, undergoes in the glue work is a steeping
in milk of lime, which removes any adhering dirt and
dissolves the blood and fleshy matter, in addition to acting
as an antiseptic in preserving the stock, if it is not to be
immediately employed. The ' liming ' is carried out in
large wooden vats some 10 feet square ^and 4 feet deep; or
in pits of the same dimensions, built into the ground and
lined with a coating of cement, the discharge being at one
corner. During the steeping, which lasts from two to ten
weeks according to the nature of the raw material, the stock
is frequently stirred with long-pronged forks so that every
part may be equally acted on by the lime. When the skins
are considered firm and free from any greasy feel, the milk of
lime is run off, and the vats or pits refilled with clean cold
water, containing a small proportion of hydrochloric acid,
which dissolves the adhering lime. This washing with
acidulated water being completed, the stock is removed to
._, ! , . j
: ; SS
, 1 ,
FIG. 19. Steeping pits and washers. Plan.
a series of washers placed near to the steeping vats or pits
and thoroughly washed with clean cold water until the last
trace of acid disappears from the wash-water.
The washers are built of wood, or are brick-lined square
pits in each of which is fitted a revolving shaft or drum with
projecting curved spokes. These on turning revolve backwards,
instead of forwards, a movement which enables the washing
to be effectively done, while at the same time the skins are
not lifted too much out of the water. In fig. 19 is shown a
plan of the steeping pits A A A A and the washers B B B.
The wet stock on removal from the washers is either hung
on racks to drain and dry, or made into bundles and pressed
40 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
between the plates of a press to squeeze out the water, and
then dried by exposure to the air.
The cleansed and dried stock is now ready for conversion
into a glue liquor, and this operation forms the second stage
of glue manufacturing.
In the extraction the method adopted varies with the
quality of glue to be made. For instance, in the manufacture
of the well-known Scotch glue the prepared stock is placed
in a loosely woven sack, which is lifted by a crane into a
circular kettle heated from the bottom and sides by a steam
coil. Water is now added, and gradually brought to
ebullition. As the animal substances decrease in bulk, fresh
additions are made, the whole being occasionally pressed
down by means of poles.
The progress of the operation is readily ascertained by
withdrawing a sample of the liquor, and if it shows a firm
jelly on cooling, the boiling has been carried to a sufficient
extent. After the mouth of the bag has been securely tied
up it is slowly raised by appropriate machinery until it
comes in contact with, or is partially coiled round, a stout
beam immediately above the kettle, which expels the fluid.
In this state it is left to drain. Meanwhile the liquor is
concentrated to a strength of 32 per cent, dry glue and then
run from the kettle to a receiving tank, from whence it is
drawn to the coolers for jellying. Having become a firm
jelly, the glue is cut out in cubic masses, which are then cut
into cakes of the thickness required by a cutting machine.
The drying of Scotch glue is of the same primitive character
as the boiling, and can only be carried on for about eight
months in the year, when temperate and -equable weather
exists. Exposed on nets stretched on a wooden framework
and built up to form a stack which is covered by a A- sna ped
roof, the cakes, by their exposure, are liable to be injured by
the least atmospheric change. For instance, if the weather
becomes too hot the glue may become soft and unshapely, so
much so as to run through the meshes of the netting on to
the cakes below ; or the drying may be so rapid that it is
prevented from contracting to its proper size without forming
numerous cracks and fissures. On the other hand, a sharp
frost will congeal the water in the cakes and thus produce
numerous cracks, which deteriorate their value. Again, in
foggy weather the moisture condensed on the surface of the
glue favours the growth of mould. These dangers have
FIG. 20. Boiling and clarifying house for skins. Section.
always to be guarded against in open-air drying, for they
render the process a very precarious one.
The cakes when about three parts dry are removed from
the netting, threaded on strings, and hung up to harden in
a dry room. Owing to the dull and soiled appearance
presented by the dried cakes, they are further dipped in
cold water and rubbed with a brush, which renders their
surfaces glossy and more attractive. In the manufacture of
other brands of hide glue, the modern method of boiling the
cleansed and dried stock along with the clarification of the
resulting glue liquors is shown in section, fig. 20. The
GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
building (in addition to the basement, fig. 22) carries a first
and second floor, part plans of which are seen in fig. 21. On
the second floor are placed the six boiling vats A, three
FIG. 21. Boiling and clarifying house for skins.
Part plan, first and second floors.
being shown in section and plan. They have a depth of 6
feet and a diameter of 5 feet, and are built of 2-inch staves
tightly bound with iron hoops. Each vat is provided with
FIG. 22. Boiling and clarifying house for skins. Ground floor plan.
a false bottom, under which rests the 2-inch steam coil B for
heating purposes. The raw material is lifted by the hoist C
to the second floor, and conveyed by a bogie to the boiling
vats. After charging with the cleansed stock, water is
GLUE CONTINUED. 43
supplied from the main D, and distributed to each vat by
the branch pipe E, the whole being gradually brought to a
gentle boil by an injection of steam through the coil B. As
the boiling proceeds, the raw material decreases in bulk,
owing to its solubility in hot water, and more is added until
a sample of the liquor shows it to be of the right strength,
which is indicated by the firmness of the jelly produced by
the sample on cooling ; or the sample may be more accurately
gauged by the glue meter, which, on insertion, registers the
strength in percentages of dry glue. When the desired
density is attained, the liquor from each vat is run through
the strainer or sieve F to a corresponding vat below, G, for
The clarifiers, of which three are shown in section, fig. 20,
and three in part plan of first and second floors, fig. 21, are
heated by the steam coils K K K, and the liquors are clarified
with potash alum in a manner similar to the treatment of
bone-glue liquors, and on opening the outlet valves H H H
they flow through the filters to the large storage tanks J J
on the basement floor, which "are heated by the steam coils
LL. From the tanks the clarified liquors are pumped to
the Yaryan evaporator for concentration.
The residual matter left in the vats after the first and
second boiling is boiled a third time to exhaust all the glue,
and the resulting solution is, without clarification, jellied for
size (containing from one-half to one per cent, of nitrogen,
mainly of a non-gelatinous nature) ; the refuse remaining
after the third boiling is used in the mixings of the manure
house after drying by exposure to the air or by waste heat.
The concentrated liquors, after bleaching, are jellied in
troughs or cast on glass slabs, as previously described, before
In France some manufacturers adopt a closed in place
of an open boiling of the skins, the operation being carried
44 GLUF, GELATINE, AND THEIR ALLIED PRODUCTS.
out in a battery of closed vessels working together in a
manner similar to a diffusion battery in a beet-sugar
manufactory. The advantages claimed for the method are
less manipulation, with lower steam consumption, along with
a higher strength of liquor and a more exhaustive extraction.
To sterilise, bleach, and lime at the same time by the use
of bisulphite of lime in place of milk of lime has been
suggested in the treatment of the raw material. No
sufficient evidence has been furnished to show that the
change, however desirable it may be, would result in a better
swelling of the glue pieces, and consequently an improved
quality of glue.
Fish Glue. Isinglass made from the bladders or sounds
of fish is the purest form of gelatine, but a strongly-smelling
glue which has considerable adhesive power is obtained to
a limited extent from the offal. In an undried state fish
contains 25 to 30 per cent, organic matter, which yields 2 to
2J per cent, of nitrogen, and it is from this body that the
glue derives its origin.
The offal is carried by conveyors to a series of washing
tanks placed overhead, and thoroughly washed with water to
remove the blood, etc. From thence it falls by gravitation
into the digesters, and is heated with 'live' steam for ten
hours. The oil and gelatinous water are drawn off by a pipe
fixed to the bottom of each digester, into tanks, the oil
skimmed from the surface, and the glue liquors clarified with
a small proportion of alum. On filtering, they are con-
centrated in open vats provided with a steam coil, to a
strength of 32 per cent, dry glue, and then bleached with
sulphurous acid. The residue left in each digester is dried
in a jacketed cylinder, and then mixed with proportions of
the double salts of potash and magnesia, to form fish-potash
Fish glue is a light brown viscous liquid with an offensive
GLUE CONTINUED. 45
odour and an acrid taste. It forms a sticky mucilage when
diluted with water, and as met with in commerce already
contains about half its weight of water, and such a liquid
is, weight for weight, only about equal to a dextrine in
viscosity. If the comparison were made on the dried fish
glue, of course, it would stand much higher, equalling some of
the second-class gum -arables.
The ash of fish glue is comparatively high, about 4 per
cent, on the body dried at 100 C. It is usually white in
colour, and contains, besides carbonates of calcium and
potassium, some 5 to 10 per cent, of phosphate of calcium.
According to Rideal, fish glue on boiling with potash assumes
a greenish-yellow colour, and absorbs about 9 per cent, of the
caustic. Liquid gums of this class are easily recognised by
boiling with Fehling's solution, when they assume a violet
colour, and by the tannic acid reaction. The unpleasant
odour and taste of fish glue is one of the objections to its use,
and the best method to remove these disadvantages is to boil
the fish glue dissolved in a little water with 1 per cent, of
phosphate of sodium, and adding '025 per cent, of saccharine.
Dissolving of Glue. The ordinary way of making a
solution of glue is by breaking the cake into pieces of a
convenient size and dissolving them with a little water in
a vessel heated by boiling water. An improved method is
to break the cake into small pieces, soak in water until soft,
drain off the water, and place the swollen pieces, which have
absorbed sufficient water to form a solution when melted,
into the glue pot, fill up the outer vessel with water, and
heat over a fire, or, better still, a Bunsen flame. When
thoroughly melted, use at once, for the hotter a glue solution
is when applied, the greater will be the breaking strain of
the two surfaces glued together. A glue solution when
allowed to cool and then re-melted has not the same tenacity
as a freshly-prepared solution. Consequently, for ordinary
46 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
work, the quantity of glue solution prepared should not be
more than is required for immediate use.
To facilitate the dissolving of glue it has been suggested to
cast the glue in strips, or pencil lengths, and dry them in
this form. By this method it is claimed that the strips will
not cake when heated with water in the glue-pot, and will
not bunch together so as to prevent liquefaction, but, due to
their form, provide interstices between the strips, through
which the heat travels.
Adhesiveness of Glue. The value of glue depends on
its adhesive power or strength. Under favourable circum-
stances, this is equal to a force of at least 715 Ibs. per square
inch. In one experiment, a force of 1260 Ibs., applied
gradually, was found necessary to separate two cylinders of
dry ash wood, the ends of which presented a surface equal to
176 square inches, and which were glued together, end to end,
and allowed twenty-four hours to set. Even this weight was
sustained for two to three minutes before the joint gave way,
and it was found, on examining the separated surfaces, that the
glue was very thin and had not entirely covered the surface.
The cohesive strength of the glue appears, therefore, in
this experiment to have been rather more than 715 Ibs. per
square inch, while the cohesive strength of the wood thus
united, in a lateral direction, was found to be only 562 Ibs.,
thus showing that if the joint had been between the sides,
instead of the ends of the pieces of wood, the wood would have
given way before the glue. In this case, however, the glue was
newly made, and the season very dry, while in some former
experiments made in the winter season with glue which had
been frequently made with occasional additions of glue and
water, the cohesive power indicated was only 350 to 500 Ibs.
per square inch. On the other hand, Mr Bovan found, in
some experiments, that the cohesive force of solid glue was
equal to 4000 Ibs. per square inch, from which it may be
GLUE CONTINUED, 47
inferred that the application of glue as a cement is capable
of much improvement, and of showing a more satisfactory
result than the above-mentioned experiment.
Glue that has been made a long time and kept in store is
found to possess greater tenacity than glue newly manu-
factured, and for the use of the joiner, pale-coloured glue is
preferred to that of a dark tint, as it produces neater and
less apparent joints. With the cabinetmaker the colour of
glue is of less importance, owing to the less frequent employ-
ment of the glue in joints exposed to the eye.
The more a body of glue penetrates the pores of the wood,
the more efficient is the joint. Glues that take the longest
time to dry are preferable to those that dry quickly, the slow-
drying glue always making the strongest joint, other things
being equal. Do not use thick glue for joints or veneering.
In all cases work it well into the wood, as painters do with
paint. In using glue, cover both surfaces of the work, except
in case of veneering. Never glue hot wood, as it will absorb
all the water in the glue too suddenly and leave only a
very little residue.
In determining the adhesive power of glue Weedenbusch
has devised a very ingenious method. He first prepares a
series of plaster prisms by mixing water and gypsum together
in the proportion of 1 to 5. These prisms are 4 inches
long, with a cross-section of J inch, and each weighs 26
grains. The glue solutions were made from 1 part of glue
dissolved in 25 parts of warm water, and the plaster prisms
were soaked in them for live minutes. Each prism is then
placed on a horizontal iron ring, in such a position as to form
its diameter, and from its centre is suspended a pan in which
weights are placed until the prism breaks. The strain it can
withstand is proportional to the adhesive power of the glue.
CHAPTER V. GELATINE.
GELATINE, which is a pure form of glue, is largely used for
culinary purposes, and consequently in its preparation the
raw materials require to be selected with great attention
to purity, and the manufacture conducted with the most
scrupulous care and cleanliness.
Gelatine is produced from white bones or hide pieces, that
derivable from the former being mainly used in the stock for
soups, etc., and as prepared gelatine, calves' foot jelly, and
Bone Gelatine. The preparation of bone gelatine
depends on the separation of the organic from the mineral
matter by an acid which dissolves the latter, leaving the ossein
in the form of the original bone. The carefully picked and
crushed bones may be degreased by a solvent, cleansed, and
then subjected to the acid treatment ; or, as carried out in
some works, the fat is recovered in the after-process of boiling
the ossein. In either case the crushed bones are conveyed to
a series of vats 10 feet square by 3 feet deep, each of which
is three parts filled and then covered with water containing
10 per cent, of hydrochloric acid. Phosphates of lime and
magnesia and carbonate of lime mainly comprise the mineral
constituents of the bone, and these salts are dissolved out by
the action of the acid, leaving the gelatine-forming ossein
intact. The steeping usually occupies about four days, the
acidulated water being renewed once during this period. The
bones now become soft, leathery, and semi-transparent, and in
this condition are sufficiently prepared for washing to remove
the acid. This is carried out by filling up each vat with fresh
water, allowing it to soak through the bones for six or seven
hours, and then draining. The washing is repeated until the
wash-water shows no appreciable precipitate on the addition
of a few drops of nitrate of silver solution. A slight turbidity
may be due to the presence of combined chlorine in the fresh
When sufficiently washed, the soft bones are thoroughly
bleached by immersion in a 1 percent, solution of sulphur-
ous acid for three hours, and then conveyed to the vats A,
fig. 20, to undergo digestion. The dissolving process is
effected in the manner described under skin glue, care,
however, being taken that the water covering the soft bones
should never exceed a temperature of 85 C. when heated by
the steam coils. Above this heat gelatinous solutions are
very sensitive as regards colour.
During the digestion, the fat if the raw bones have not
undergone a degreasing process rises to the surface and is
carefully skimmed off from time to time, the skimmings
being subsequently washed with hot water, before filling
A second digestion is necessary to practically exhaust the
gelatinous matter, and the first and second runnings from
the vats, having a density corresponding to 20 and 12 per
cent, dry glue respectively, as indicated by the glue meter,
then flow to the clarifiers and are treated with a small
quantity of potash alum ; from thence the liquors pass
through the filters for concentration in the Yaryan eva-
porator to a jellying strength of 32 per cent, dry glue.
To obtain the colour necessary for a high-grade gelatine,
the concentrated liquors undergo a further bleaching in the
50 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
tanks EE, fig. 12, and are then run on to the glass slabs to a
depth of half an inch for cake and quarter of an inch for
As a commercial product leaf gelatine is coloured with
dye-stuffs to suit certain trade requirements. Carmine is
a colour often employed for this purpose, and aniline colours
are also used in the proportion of 1 ounce of colouring matter
dissolved in a small quantity of glycerine to every 16 Ibs. of
liquid gelatine, the solution being strained through linen
cloth and then mixed with the concentrated liquors before
jellying. In the production of coloured leaf gelatine the
liquors are not bleached after concentration. The method
of manufacturing gelatine varies ; for instance, some French
makers substitute phosphoric for hydrochloric acid in
dissolving the mineral matter of the bone. For this purpose
the carefully picked bones are dried at a temperature not
exceeding 100 C. and then pulverised to a coarse powder in a
mill. The powdered bones are then introduced into a circular
vat provided with a stirrer, and the phosphoric acid, of 12
Tw. strength in the proportion of 1 cubic foot by measure
to each 10 Ibs. of raw material, is well stirred in the mass.
The acid decomposes the carbonate of lime with evolution of
carbonic acid, and converts the insoluble phosphates of lime
and magnesia into soluble acid phosphates. The stirring is
continued until the carbonic acid is wholly driven off ; and
on allowing the mixture to stand for a time, the crude
gelatine falls as a sediment to the bottom. After the super-
natant liquor has been syphoned off and precipitated with
sulphuric acid to liberate the phosphoric acid for use again
as a dissolving agent, the sediment is well washed with cold
water and then treated with hot water of a temperature not
exceeding 85 C., which dissolves the crude gelatine ; the!
liquor is afterwards clarified, bleached, and concentrated in
the usual way.
' Osseine ' is a French preparation from bones, and is brought
into the market in a dry and concentrated state for the
manufacture of gelatine. In using it the product is soaked in
water for forty-eight hours, the water being renewed every
twelve hours. When it is thoroughly swollen, the 'osseine'is
well washed with water until the washings are absolutely
clear, and yields a gelatine quite clear and without any smell.
The washed product is next bleached for one hour in a
bath of sulphurous acid of 1 Tw. strength, and then finally
dissolved at a temperature of 85 C. in a wooden vat fitted
with a copper steam coil and provided with a double
wooden bottom to distribute the heat. The gelatinous liquor
is concentrated and jellied without clarification.
Animal charcoal is a powerful decolorising agent, and
its use as a filtering medium has met with some success in
obtaining a white gelatine from low-grade bone products,
and also in improving the colour of the gelatine obtained as/? ^
a secondary product in the manufacture of neat's-foot oil. _
Skin Gelatine. The preparation of gelatine from the
parings and cuttings of hides varies but little from the
process as described in the manufacture of skin glue. In
some factories, instead of using lime only in steeping the hide
pieces, a mixture of caustic soda and lime made into a milk
with water is sprayed over the mass in the pits. The use
of caustic soda facilitates the saponification of any fat present
and the dissolving of the fleshy matter.
Before the digestion, which is effected at a temperature
not exceeding 85 C., the hide pieces, on removal from the
lime pits, are washed free of any alkalinity, and are then
bleached by sulphurous acid to destroy any injurious
colouring matter. To completely exhaust the gelatinous
matter during digestion, three ' boilings ' are generally
required, the first and second runnings being treated for
gelatine, while the third is simply filtered for size.
52 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
A very fine water-white leaf gelatine is produced by
cutting the jelly into small pieces, washing well with cold
water and re-melting at 80 C., then pouring the liquor on
the ' glasses ' to the depth required.
Seaweed Gelatine. A product hardly distinguishable
from gelatine, and used for many purposes in the arts
similarly to that body, is known as seaweed gelatine, and is
produced from a genus of weed to which the name of
Laminaria is given. When macerated with water, about 33
per cent, of the weight of the air-dried weed is removed. The
residue, when digested with carbonate of sodium, is partly
dissolved, forming a soluble compound of sodium alginate.
On filtering, the filtrate is mixed with hydrochloric acid,
which liberates the alginic acid. The acid is washed,
bleached, and re-dissolved in alkali, and by concentration in
a vacuum pan and then running on glass plates or porcelain
slabs, the sodium alginate is obtained in the form of trans-
parent flexible sheets like gelatine and having the same
colour, but they are not gelatinous. These sheets can be
rendered insoluble without altering their appearance by
immersion in dilute hydrochloric acid; they can also be
readily coloured like leaf gelatine.
In America a gelatine is made from seaweed, called by
the native name of Tengusa. The weed is carefully dried
and afterwards boiled so as to form a glue-like decoction,
which is strained off and put into square boxes. When cool
it forms a thick jelly, which can be easily divided into
squares a foot in length. The manner in which the surplus
water is removed is very ingenious. The jelly prisms are
exposed in the open air during a cold night and allowed to
freeze. During the day the sun melts the ice to water,
which runs off, leaving behind what might be termed a
skeleton of white horny substance, which is extremely light,
and easily dissolved in hot water ; when cool, it again forms
a stiff jelly. This article can be applied to many purposes
for culinary purposes, for making bonbons and jellies, for
clarifying liquids, as a substitute for isinglass, for making
moulds used by the plaster-of-Paris workers, for hardening
the same material in short, as a substitute for all kinds
of gelatines, over which it has the advantage of producing a
Comparison of French and British Gelatines. The
ash and water absorptive-power are indicative of the value of
a gelatine, and in the following table a comparison is made
of gelatines of French and British manufacture.
Water absorption by
28 '34 grams of Substance
Coignet's gold label, .
1 per cent. : 340 '08 grams.
Coignet's special, . .
Nelson's No. 1, . .
Swinburne's No. 2, . )
Patent isinglass, . . (
Cox's packet gelatine,
The Behaviour of Gelatine with certain Salts.-
Gelatine is unaffected when in contact with solutions of lead,
tin, nickel, cobalt, manganese, aluminium, magnesium, and
other metallic salts. With a solution of chloride of barium
it is completely dissolved. It is also, although to a smaller
degree, soluble in chloride of strontium. Other chlorides,
such as those of potassium, sodium, and calcium, do not act
in the same way, nor do their iodides or bromides. With
a solution containing 15 per cent, chloride of barium, the
solubility is so great that sufficient gelatine may be dissolved
to render the solution syrupy in consistence. The liquid
keeps well, and does not decompose under the action of air.
54 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
Allowed to evaporate spontaneously, it leaves behind a solid
white substance which, when examined under the microscope,
shows itself to be composed of an amorphous mass of
filaments mixed with fine crystals of chloride of barium, but
it does not appear that any combination has taken place.
This solid substance dissolves in water completely. When
exposed to light, gelatine is rendered insoluble in the presence
of bichromate of potassium. Gelatine is precipitated from its
solution by chloride of iron both in the light and in the dark.
CHAPTEE VI. SIZE AND ISINGLASS.
Size. As a cheap and easily workable agglutinant, size finds
a ready use with calico-printers, painters, decorators, and in
the carpet, straw-hat box, wallpaper and other trades. Size
is undried glue, and exists as a tremulous jelly, possessing all
the adhesive properties of the latter, but in a much less
In a sense, size is a bye-product in the manufacture of
glue and gelatine, for the third liquors in the exhaustion of
the raw material only are used for this purpose, and these,
if converted into either of the above agglutinants, would yield
an inferior product ; consequently it pays the manufacturer
better to gelatinise it and to sell it in this form without
drying. In small works exclusively making bone size the
manufacturer with no benzene or glue plant at his disposal
simply washes the rough bones in a revolving drum, and
after crushing in a mill, feeds the broken pieces into an
elevator, which lifts and discharges them into one or more
digesters heated by ' live ' steam. When the bones are
sufficiently acted on, the steam is turned off, and the grease
and gelatinous liquor are blown through the outlet pipe to
an overhead tank. After separating the fat, which is
subsequently well washed with hot water to remove the
impurities, the gelatinous liquor is filtered to separate any
suspended matter, and then evaporated in a wooden vat
fitted with a steam coil to the density required.
56 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
During the evaporation a moderate charge of sulphurous
acid solution is sometimes added to improve the colour.
Size is brought into the market as (1) common size; (2)
medium size; (3) best size. The first contains 25 per cent,
glue and 75 per cent, water ; the second, 30 per cent, glue
and 70 per cent, water ; and the third, 38 per cent, glue and
62 per cent, water. For exportation a stronger size is
made in three grades, No. 1 containing 40'5 per cent, glue,
No. 2 44*5 per cent., and No. 3 49 per cent., the liquors
being evaporated to these densities before jellying.
Glue or gelatine in a dried state is a very stable body, but
in the form of a jelly it soon ferments, becoming sour and
mouldy, unless some preservative agent is used to prevent
decomposition. For this purpose sulphate of zinc is
principally used ; boracic acid, and also a preparation known
by the name of * Salinfer,' have been used with good effect.
These preservatives are added to the liquors before running
into the casks to set.
In sorting the cakes of glue before packing, a number are
always found unsuitable, owing to their having become
twisted during the shrinkage in drying, or not equal to the
standard as regards colour. These defects, while not lowering
to any appreciable extent the value of the cakes as an
agglutinant, yet affect their selling power. They now find a
ready sale in a powdered condition as ' Concentrated Size ' or
' Glue Powder,' the cakes being ground, sifted, and graded by
Isinglass. The purest form of commercial gelatine is
isinglass. This valuable product is obtained from the
swimming bladder or sound of various species of fish, of
which the sturgeon yields the finest quality. Isinglass is
brought into commerce under the name of pipe, lump,
honeycomb, purse, leaf, and other designations, and these
different kinds are due to the method of preparing the
SIZE AND ISINGLASS. 57
bladder. For instance, pipe, purse, and lump isinglass
consists of the sound desiccated, but unopened ; while in the
leaf and honeycomb kinds the bladder is cut open and then
dried unfolded. When the cut bladder is folded and dried,
the product is known as book isinglass, while in the ribbon
isinglass it is rolled out. From Kussia is obtained the finest
quality of isinglass in the form of leaf, book, and long and
short staple, the four varieties principally coming from
Astrakhan and Taganrog. In preparing Russian isinglass,
the swimming bladder is first cleansed of the mucus and
blood stains by immersion in hot water, then cut open
longitudinally and exposed to the air with the inner delicate
silvery membrane upwards. When dried this fine membrane
is removed by beating and rubbing, and the swimming bladder
is made into the different forms by twisting or folding.
Brazilian isinglass is imported from Para and Maranham
in the form of pipe, lump, and honeycomb. Pipe Brazilian
isinglass is prepared by drying the swimming bladder
unopened. When dry, each bladder is from 10 to 12 inches
long and 2 to 2J inches broad, weighing about 5 ounces.
Lump Brazilian isinglass consists of two swimming
bladders placed side by side, considerably separated at
one end, but communicating with each other at the other
extremity. An average-sized lump will weigh about 6J
ounces. Honeycomb Brazilian isinglass is the lump
variety split open. The latter is sometimes softened and
rolled out into thin strips, and is then known as ribbon
isinglass. Brazilian, and also the isinglass imported from
Hudson's Bay, Penang, India, etc., is the product of different
species of fish, and is darker in colour and less soluble than
the Kussian variety. As received in this country, isinglass
is a hard and tough substance, and for many purposes it
requires to be cut into fine shreds to facilitate its solution.
According to Watson Smith, there seem to be only six
58 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
isinglass cutters in England, all being domiciled in London.
The crude isinglass is first sorted, soaked in water until it
becomes a little pliable, and then trimmed. Sometimes it is
just pressed by hand on a board with a rounded surface ; at
others it is run once between strong rollers to flatten it a
little and make the dark and dirty spots accessible to the
knife, the top of the roller being used to bend the pieces on.
The cuttings are sold separately as an inferior grade. The
next process is that of rolling. Very hard steel rollers,
powerfully and accurately adjusted, are used. They are
capable of exerting a pressure of 100 tons. Two are
employed, the first to bring the isinglass to a uniform thick-
ness, and the smaller one, kept cool by a current of water,
to reduce the isinglass to a little more than the thickness of
writing paper. It is very curious to see the thick, tough
pieces gradually spreading out under the rollers and folded
and rolled like puff pastry, till the separate pieces so unite
themselves that no joint can be seen, and the mass is reduced,
under the coarse rollers, to what looks like semi-transparent
millboard. From the finer rollers it comes in a beautifully
transparent ribbon, many yards to the pound, 'shot' like
watered silk, in parallel lines about an inch broad. It is now
hung up to dry in a separate room, the drying being an
operation of considerable nicety. When sufficiently dried,
it is stored till wanted for cutting, or is sold as ribbon
isinglass to those who prefer this form.
The machines for cutting are well and accurately made,
and are so adjusted that they slice pieces off a sheet of paper
without bending it in the least. For the fine ' cut ' isinglass,
these machines are run at a great speed, 2000 to 2500
revolutions, making 10,000 to 12,000 cuts in a minute. It
takes an hour to cut 5 Ibs., so that every pound would contain
100,000 to 125,000 separate fibres, if none of them were
broken. Isinglass is used in but few industries. The largest
SIZE AND ISINGLASS. 59
quantity is used by brewers and wine merchants for clarifying
purposes. This property is extraordinary, for gelatine, which
is chemically the same thing, does not possess it. One
theory is that the tenacious mucilage shaken with the liquid
gradually settles to the bottom, entangling all floating
particles as it sinks. Another suggestion is that a very
delicate fibrous network remains after the isinglass is
dissolved, and entangles the particles in the way that the
mucilage is supposed to act. Many varieties, generally the
lower brands, are used for this purpose. Some brewers use
it in the natural state, others prefer it manufactured into a
fine or wide strip, which dissolves quicker and suffers no
waste. At present Penang is the favourite kind. Eussian
long staple isinglass is used only by the Worcestershire
farmers for clarifying their cyder. In spite of its costliness,
Scotch brewers prefer Russian leaf. For clarifying purposes
the isinglass is 'cut' or dissolved in acid, sulphurous acid
being used as the solvent, owing to its preservative nature.
When reduced to the right consistency, a little of the solution
is placed in each cask before sending it out for consumption.
Sole skins are sometimes used as a substitute for isinglass.
They are only to be had in winter, the supply is uncertain,
and they have not the strength of the Penang varieties.
Next to the brewers' demand comes that of the cook, who
uses it for making jellies, thickening syrups, and stiffening
jams. Russian takes the highest position, owing to its
superior strength and nourishing properties. Isinglass being
the purest natural form of gelatine, a very fine article has
long been known in the market as ' patent isinglass/ which
is a gelatine of high quality. It does not, however, possess
the clarifying power of the natural article, but is equally
used for culinary and confectionery purposes. Outside the
demands of the brewer and cook, isinglass has but a limited
use in the arts. In textile works isinglass is used along with
GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
gum to give lustre to ribbons and other silk articles, while
as a substitute for glass it answers well for lamp shades.
Isinglass is also used in preparing a substitute for Indian
ink ; for this purpose three parts of isinglass are made into a
size by dissolving them in six parts soft water. In another
vessel, 1 part of Spanish liquorice is melted in 2 parts of
soft water, over a fire, and then saturated with 1 part of
ivory black. The two solutions are mixed together and
stirred well. This mixture is evaporated to a thick syrup,
and this is run into a leaden mould which has been slightly
oiled, and allowed to set firm. The product is much of the
same nature and applicable to the same purpose as Indian
ink. As an agglutinant, isinglass is used in the form of
diamond cement by dissolving two parts of it in four parts of
spirit of wine, the solution on cooling yielding an opaque,
milk-white, hard jelly. It also dissolves in strong acetic acid,
forming a powerful cement, much used for repairing glass,
pottery, and similar small objects.
The well-known court plaster is made by brushing a
solution of isinglass, mingled with a small quantity of
tincture of benzoin, over black sarsenet.
Isinglass is not suitable for photographic work, on account
of its great solubility and inferior tenacity. The composition
of isinglass, so far as required for commercial purposes, is as
In parts per 100.
Fine Russian, . 1 '2
Russian pipe, . *8
Lump Brazilian, . 1 '4
Royal northern bladder,
Siberian purse, .
Cayenne Brazilian, .
CHAPTER VIL EFFLUENTS : MARROW BONES
Treatment of Effluents produced in Glue and Gelatine
making. In face of the growing stringency of the public
authorities in dealing with trades' effluents, the disposal of
the waste and wash waters from the various operations in
the factory becomes an important matter. These waters
contain a large proportion of suspended and dissolved
mineral and organic matter, and their discharge into a water
course without treatment of any kind would form a source
of pollution, rendering the manufacturer so offending liable
to severe penalties under the Rivers Pollution Prevention Act.
Formerly the effluents were treated in a very primitive
way by running them into roughly-made ponds, whence,
after a partial subsidence of the suspended matter, the still
muddy liquors were allowed to percolate through the soil.
An improvement on this was the system of nitration through
layers of coke and sand, which, while retaining the suspended
matter, failed to remove any in a dissolved state.
To meet the high standards of purity enforced by many
County Councils, some form of treatment which would
remove both the soluble and insoluble impurities became
necessary. This is now carried out chemically by a method
of precipitation with soda-ash and alumino-ferric, the applica-
GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
tion of these reagents in the treatment of the effluents being
shown in figs. 23 and 24, which illustrate the Archbutt-
Deeley installation for the purification of waste and wash
The Chemical Trades Journal, in describing this apparatus
and its working, says that it consists of a large tank A. which
may be constructed of brick, concrete, or iron. The waste
water to be treated is admitted at the inlet B. While the
tank is filling, the chemicals required for precipitation are
weighed out and boiled up with water in the small chemical
FIG. 23. Archbutt-Deeley purification plant. Section.
tank C by means of live steam. When the tank is full and
the inlet valve has been closed, steam from the boiler is
admitted to the blower D, causing a current of water to
circulate through the rose E, the threeway tap F, down the
vertical pipe, and back into the tank through the perforations
in the upper row of horizontal pipes G. On opening the small
tap H the prepared chemical solution is slowly drawn into
the circulating current and uniformly diffused throughout
the body of water in the tank. The tap I is next opened to
admit air through the pipe at the top of the blower, and by
reversing the threeway tap F this air is forced through the
EFFLUENTS : MARROW BONES AND BYE-PRODUCTS.
perforations on the under side of the lower row of pipes J.
From these it rises in streams of bubbles, stirring up some of
the precipitate from previous operations, which, when diffused
throughout the water, carries down the flocculent particles
of freshly-formed precipitate. Any residual virtue in the
precipitant from the previous batch is also utilised, thus
effecting considerable economy in chemicals. Steam is then
turned off, and in about thirty minutes to one hour nearly all
FIG. 24. Archbutt-Deeley purification plant. Plan.
the precipitant will have settled to the bottom of the tank,
and the supernatant water, even to a depth of six feet, will
not average more than about one grain of suspended matter
per gallon. The clear water is drawn off by the floating
discharge pipe K to a receiving tank L, from whence it may
be run to a stream or sewer.
The precipitated sludge has a manurial value when in a
dried state, due to the nitrogen and phosphate of calcium it
contains. To prepare it for use in the manure shed, it is
64 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
pumped into a powerful press which removes fully 90 per
cent, of the water, the pressed cakes being subsequently
dried by waste heat, then pulverised by passing through a
disintegrator, and used in the compounding of low-grade
On the raw bones entering the works, the leg and thigh
bones, known as ' marrows ' or * knuckles/ are separated
from the heads, ribs, etc., and undergo a treatment different
to that of the latter. In the first instance, the * marrows '
are not treated with a solvent ; and secondly, they are only
partially degreased and degelatinised in the slow boiling
they receive. The object is to remove only a portion of
the fatty and gelatinous matters, leaving the bone firm
and hard so that it can be turned in a lathe. If the boiling
is excessive and prolonged, the bone becomes chalky and soft,
and thus useless for conversion into the many articles of
Treatment. In working the ' marrows ' the ends are
sawn off by a circular saw to open out the core and thus
facilitate the removal of the fat in the after-process of boiling.
The cut bones are now steeped in cold water containing
1 per cent, of salt for three or four days, to separate the
fibrous matter derived from the fine bloodvessels. After
washing with water they are conveyed to a large circular
vat provided with a steam coil and a double bottom to
distribute the heat. The bones are covered with water, which
is gradually brought to a simmer and maintained at that for
six hours. During the heating all the fat in the core of the
bone is removed along with a part of the gelatinous tissue,
trhe former rising to the surface, while the latter is dissolved
in the hot water. The fat is skimmed off from time to time,
bleached, and then used for the making of high-class toilet
EFFLUENTS : MARROW BONES AND BYE-PRODUCTS. 65
soaps, or, in the unbleached state, the fat oil is expressed, and
used in adulterating neat's-foot and other highly-priced oils,
while the residual stearine is of value to the candlemaker.
Composition of Extracted Fat. -- The following
analyses represent the composition of the bleached fat :
In parts per 100.
Water, ... -58 '94 76
Organic matter other
than fat, . . "04 -07 '01
Mineral matter, . '11 '15 '23
Fat, . . 99-27 98'84 99'00
100-00 100-00 100-00
The mineral matter is mainly phosphate of lime.
The water, which has extracted 8 to 9 per cent, of
gelatinous matter, is chiefly used for the preparation of high-
class size for cardboard boxmaking, and with this object it is
run through a filter of coarse woven calico into a receiving
tank, the filtration removing the phosphate of lime and
other suspended impurities. If further clarification is
necessary to remove any soluble organic matter other than
glue, it is carried out in the tank in the manner described
under ' bone glue,' with a small proportion of alum. On
filtering, the liquor is run into a vat heated by a steam coil,
half a bucketful of sulphurous acid, 3 Tw. strength, added,
and then evaporated to a density of 32 per cent, dry glue as
registered by the glue meter. The partially degreased and
degelatinised bones are now removed from the boiling vat,
and each one is scrubbed with a brush to detach any meaty
matter, then placed on a rack and air-dried.
Uses. The dried bones are used for manufacturing
buttons, knife-handles, spoons, paper-knives, and many fancy
articles of daily use ; the residual trimmings in cutting the
rough buttons from the bone slabs are used for gelatine
66 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
making ; and the dust formed in drilling the eyes is used as
a food for poultry and dogs.
Partially Degelatinised Bones and their Conversion
into Animal Charcoal, etc. With a carbonising plant at
his disposal the manufacturer is well advised if he only
partially degelatinises the degreased bones that is, extracts
only half of the nitrogenous and carbonaceous matter as
glue and carbonises the remainder to animal charcoal, using
the tar, ammoniacal liquor, and uncondensed gases forming
the bye-products ; the two former for the production of bone
pitch and sulphate of ammonia respectively ; and the latter,
after purification, for illuminating or motive purposes.
Carbonisation. Animal charcoal made from partially
degelatinised bones is of a deep black colour, and has a
metallic ring when struck. As it contains the limit of fixed
nitrogenised carbon (10 to 11 per cent.) necessary for a high-
grade charcoal, it is fully equal to the product made direct
from undegelatinised bones. The carbonisation is effected
in a series of retorts, 12 feet long, fixed horizontally in a
furnace, and heated from a fire beneath. The retorts are
made of cast iron, and five are fixed in each furnace, forming
what is known as a ' bench/ At the open end is fixed the
frame, which carries the door swung on a hinge. Bolted on to
the upper surface of the frame is the up-take pipe leading
to the hydraulic main, containing a layer of ammoniacal
liquor, into which it dips, and thus effectually closes the
retort against any back-rush of gases during drawing and
charging. Each retort takes a charge of 5 cwts., which
requires twelve to thirteen hours for complete carbonisation.
When ready for withdrawal the door of the retort is
slightly loosened by turning a lever, the escaping gases are
burnt, and in a few minutes the internal pressure is destroyed,
allowing the door to be opened widely with safety.
The red-hot charcoal is rapidly withdrawn by the retort-
EFFLUENTS : MARROW BONES AND BYE-PRODUCTS.
man into a canister, covered with a lid, and rolled to the
cooling shed of the mill, where the lid is made airtight by a
luting of charcoal dust and water, and the canister allowed
to cool for twenty-four hours.
Milling. When cooled, the charcoal is watered, and
then conveyed to the mill, undergoing first a cutting into
small pieces by two revolving toothed wheels, and then a
riddling action in revolving cylinders covered with a No. 7
wire cloth. The fine and coarse particles passing from the
cylinders are coarsely ground and then passed to a second
set of cylinders or riddles covered with a 60-mesh wire
cloth, the dust coming through the cloth being bagged and
used in the manufacture of superphosphates and ivory black.
The clean charcoal is then conveyed to a third set of riddles
covered with wire cloth to suit the grade of charcoal required,
and finally bagged as grade 14/60, 12/20, 20/30, or any other
grade required by the buyer.
The grading of these charcoals is seen as follows :
Size 14 .
Size 12 .
, 20 .
, 30 .
, 40 .
, 50 .
, 60 .
. . 2'88
. . 87-15
. . 8-39
. . -55
. . -46
. . -29
Size 20 .
,. 40 .
Dust . .
. . 2-14
. . 71-85
. . 15-63
. . 6-17
. . 3-14
. . 1-07
I AA .AA
Dust . .
In a high-grade charcoal the amount passing through a
riddle, size 40, should not exceed 2 per cent.
Tarry and Ammoniacal Liquors. The tarry and
ammoniacal vapours leaving the hydraulic main are passed
68 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
to the condensers, consisting of a series of pipes vertically
placed, through which the hot gases ascend and descend,
until their temperature is reduced to 85 F., this reduction of
temperature condensing the vapour, which, as a liquid, runs
into the separating tank ; from the difference in gravity the
tarry matter rises to the surface and is floated off to the tar
well. The ammoniacal liquor is pumped from the separating
tank to the ammonia still, and the ammonia distilled over
by steam heat into the ' sulphate box, ' neutralised with
sulphuric acid to saturation point, when the sulphate of
ammonia separates out in fine particles or crystals falling to
the bottom of the box, and at intervals are ' fished out ' by a
ladle, drained, and dried by air exposure. From the well the
tar is pumped to a still heated by a fire underneath, and on
distillation the volatile products, after condensation, yield an
oily liquid to which the term of ' bone oil ' is given, while
the residue, on running from the still, solidifies as bone pitch,
and is used mainly in the manufacture of black varnishes,
Brunswick black, ivory black, etc. The uncondensed gases
from the condensers are purified by passing over lime, stored
in a gas-holder, and used for motive or illuminating purposes.
Yield and Composition. The yield of animal charcoal
amounts to 55 or 60 per cent, of the bones retorted, and
the following analyses, made by the author, represent its
In parts per 100.
Moisture, .... 7'41 6*33
Carbon (nitrogenised), . 10'49 1116
Phosphate of calcium, . 74'17 72'64
Carbonate . 5'96 7'97
Sulphate . 1-22 -89
Oxide of iron, . . . 0'06 -14
Sand, -69 -87
CHAPTER VIIL LIQUID AND OTHER GLUES,
FOR many purposes an agglutinant which permanently retains
its liquidity is found more suitable than the ordinary cake
of glue which requires to be melted in water before it is
available for use. To supply this want we have the numerous
soluble and liquid glues, formed by adding to the glue, when
in solution, some ingredient which, while it destroys the
gelatinising property, does not impair its adhesiveness.
The following collection of recipes is large ; only those have
been selected which were believed to be trustworthy and
valuable. They were taken from periodical literature and
(1) Possessing great resisting power.
Clear gelatine, . . . 100 parts
Glue, . . . . . 100
Alcohol, .... 25
Alum, .... 2
Mix the whole together, and then add 200 parts of 20 per
cent, acetic acid, and heat on a water-bath for six hours.
(2) Improved liquid glue. Dissolve 3 parts glue in 12 to
15 parts saccharate of lime. On warming, the glue dissolves
rapidly and remains liquid when cold, without losing its
70 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
strength. Any desirable consistency may be obtained by
varying the amount of the saccharate.
(3) Dissolve 2 parts fine glue in 4 parts water heated over
a water-bath. When dissolved, add 2 parts glacial acetic acid.
(4) Dissolve 16 parts of best white glue in 32 parts water
by heat; when dissolved, add 4 parts dry white lead, and
stir well. Add the alcohol, and continue the heat for a few
minutes ; lastly, pour into bottles while it is still hot.
(5) A liquid glue of great strength and useful for a variety
of purposes is made by dissolving 30 parts of good glue in a
solution prepared by melting in 20 parts dilute phosphoric
acid 4 parts carbonate of ammonium. The glue is stirred
into the solution, heated to 70 C. until dissolved, and the
mixture allowed to cool.
(6) For printing purposes, a liquid glue is prepared by
dissolving 28 parts of a good quality of glue in 56 parts of
hot water. On complete solution 28 parts of fused chloride
of magnesium are added, and stirred well until melted. As
a preservative, 1 part of boracic acid is added, and the
mixture is allowed to cool for twenty-four hours, when it is
ready for use.
(7) Fifty parts of glue are dissolved in 125 parts of hot
water. When melted, add 30 parts chloral hydrate, stir
well, and allow to cool for forty-eight hours. The solution,
which remains perfectly fluid, forms an excellent adhesive for
(8) Dissolve 3 parts of good glue in 5 parts nitric ether ;
the ether will only dissolve a certain amount of glue, there-
fore the solution cannot be made very thick; on complete
solution it will be about the consistency of syrup, and is
much more tenacious than glue made with hot water. It is
improved by adding a few pieces of indiarubber, cut small,
and the solution is then allowed to stand a few days, stirring
LIQUID AND OTHER GLUES, CEMENTS, ETC. 71
(9) A very strong liquid glue is prepared by dissolving
4 parts of glue in 15 parts warm water, allowing to stand,
and then adding f part hydrochloric acid and ^ part sulphate
of zinc. Heat at 90 C. for ten to twelve hours. It remains
liquid after cooling. Used for wood, crockery, and glass.
(10) Russian liquid glue. Soften 50 parts best Russian
glue in 50 parts warm water, add slowly 3 parts nitric acid
and 3 parts sulphate of lead. Stir well, cool, and bottle.
(11) Brand makes an animal glue by dissolving 60 parts of
borax in 100 parts of water, adding to the solution when
boiling 4 parts of 90 per cent, calcined potash, and stirring
intimately the mixture in 1000 parts of glue liquor of 12 B.
(1) Dissolve 16 parts of good glue in 24 parts methylated
spirit, or in the same proportion of skiin milk, then add
4 parts of powdered lime, and stir well.
(2) Mix 20 parts of quicklime with 4 parts of linseed oil.
Thoroughly stir the mixture, then heat until quite thick, and
spread on plates. It will set in a hard mass, and can be
melted over a fire like ordinary glue.
(3) Soak 10 parts of glue in the same quantity of water,
and remove it before it has lost its primitive form. Then
dissolve the swollen glue in 8 parts linseed oil over a slow
fire until it forms a jelly. This glue may be used for joining
many materials. In addition to strength and hardness, it
resists the action of water.
(4) Dissolve 12 parts of glue in an equal weight of hot
water, then add 3 parts of yellow resin and continue the heat
until melted ; finally, add 4 parts of turpentine, and mix
thoroughly together on a water- bath.
(5) Dissolve in 16 parts strong methylated spirit 1 part
each of sandarac and mastic ; next add 1 part turpentine.
72 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
This solution is then added to a hot thick solution of glue,
prepared by dissolving 12 parts of glue in 16 parts of water
by steam heat. The mixture is now filtered, while hot,
through cloth or a sieve.
(6) One hundred parts of a thick solution of glue, prepared
by dissolving glue in an equal weight of hot water, is mixed
with 50 parts linseed oil varnish and 10 parts litharge. Heat
for ten minutes, and use while hot.
(7) Dissolve 10 parts of glue in 15 parts of hot water,
and add bichromate of potassium in the proportion of ^ of
the glue taken. There is no better glue for wood in contact
with water than bichrornated glue. Allow it to harden
(8) Soak 10 parts of glue in water until it is soft ; then
dissolve it in the smallest possible quantity of proof spirit
by the aid of a gentle heat. In 10 parts of this mixture
dissolve 1 part of gum ammoniacum, and, while still warm,
add 1 part of mastic dissolved in 3 parts rectified spirit ;
stir well. It is essentially a solution of glue in mastic
(9) Glue may be rendered insoluble and thus waterproof,
by means of tannic acid dissolved in a small quantity of hot
(10) The so-called marine glues found in commerce
contain no glue ; they are mixtures of benzene or naphtha
with shellac, indiarubber, or asphaltuin. Jeffrey's marine
glue is prepared by dissolving 1 part of indiarubber in
4 parts of crude benzene, and mixing with the solution 2
parts shellac, by heat. The waterproof character of this
preparation, its slight elastic flexibility, the ease with which
it is applied, when warm, and the promptness with which it
sets on cooling, makes it a most useful substance in many
applications to house construction and furniture, as well as
on board ship, where it was originally intended to be chiefly
LIQUID AND OTHER GLUES, CEMENTS, ETC. 73
employed. Another preparation is made by dissolving 1 part
caoutchouc and 2 parts asphaltum in 4 parts naphtha.
White or Russian glue. White glue is prepared by
forming a concentrated solution of glue (5 parts glue to
8 parts water), and, while hot, adding 1 part of white oxide
of zinc and 1 part oxalic acid to every 20 parts of the glue
solution. Allow mixture to form a jelly, and then dry in
the form of cakes.
Tungstic glue. Tungstic glue has been suggested as a
substitute for hard indiarubber, as it can be used for all the
purposes to which the latter is applied. It is prepared by
making a concentrated solution of glue (5 parts glue and
8 parts water), and adding to this a mixture of tungstate
of sodium and hydrochloric acid in the proportion of 2 per
cent, of the dry glue taken. A compound of tungstic acid
and glue is precipitated, which, at a temperature of 60 C.,
is sufficiently elastic to be rolled out into very thin sheets.
Chrome glue. To every 100 parts of a concentrated
solution of glue (5 parts glue and 8 parts water), while hot,
add 5 parts of dehydrated bichromate of potassium. When
dissolved, allow the solutions to set to a jelly ; cut into cakes,
Portable glue. A very convenient form of glue is known
as portable or mouth glue. It is prepared by adding 1 part
of sugar to every 4 parts of fine pale glue dissolved, and
continuing the heat until the sugar is melted. It is then
poured on a slab or plate, and, when cold, cut into squares.
The glue is easily softened by the tongue, and is, for many
purposes, very handy.
Frozen glue. A form of glue preferred by many users in
America is prepared as follows : The glue, while in the
form of a jelly, is sliced and placed on nets, and allowed to
freeze by natural cold. The process can only be conducted in
cold weather. The product is porous and much more bulky
74 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
than ordinary glue, but it is a better article, and dissolves
Elastic glue. An elastic and flexible glue is prepared by
dissolving 10 parts of fine pale glue in 15 parts hot water,
and then adding 7 parts of glycerine. Heat until the water
is driven off; pour on to a marble or glass slab to cool, and
cut into blocks about 12 inches square. Elastic glue is of
value in the bookbinding trade, for in its use bookbinders
get rid of that cracking noise so often heard when opening new
books in which ordinary glue has been used in the binding.
Cements. For binding or cementing purposes, many
preparations in which glue or gelatine forms the leading
ingredient are used.
The following are the cements chiefly used :
Glue for repairing broken glass. Dissolve fine glue in acetic
acid to form a thick syrup. Another preparation is made by
dissolving equal parts of isinglass and glue in hot water, and
straining through coarse linen. Then add a little alcohol, and
evaporate by steam heat to such a consistency that, when
cold, it will be dry and hard.
Glue for ivory and lone. Equal parts of isinglass and glue
are dissolved in hot water to a concentrated solution, and
then 5 per cent, of zinc white is added to bring the whole to
the consistency of molasses.
To glue labels to iron. Make a paste of rye, flour, and glue,
formed by adding these ingredients to hot water, and stirring
well until the glue has dissolved. To every 16 parts of the
paste add 1 part linseed oil varnish and 1 part of turpentine.
To glue leather to iron. Paint the surface of the iron with
a lead pigment, say white lead and lampblack ground up in
oil. When dry, cover with the following cement: Take the
best glue, soak it in cold water till soft, dissolve it in acetic
acid with a moderate heat, and then add turpentine in the
proportion of J of the bulk, and thoroughly mix. By means
LIQUID AND OTHER GLUES, CEMENTS, ETC. 75
of a further addition of acetic acid it is brought to a con-
sistency to enable the solution to be spread with a brush.
It is applied while hot, and in the application the leather
is drawn on quickly and pressed tightly to its place.
Glue for leather goods. This glue, though complex in
composition, gives good results. Eight parts of rye spirit are
diluted with 8 parts of water, and the mixture is made into
a paste with 2 parts of powdered starch. One part of glue is
dissolved in the same amount of hot water; to the glue
solution 1 part of turpentine is added, and the solution is
thoroughly incorporated with the paste.
To glue leather to metals. One part crushed nutgalls is
digested for six hours with 8 parts of distilled water, and
strained. Glue is macerated in its own weight of water for
twenty-four hours, and then dissolved by heat. The warm
infusion of nutgalls is spread on the leather, and the glue on
the roughened surface of the warm metal. The moist leather
is then pressed upon it, and dried.
G-lue for tablets. Soak 25 parts of best glue in the same
proportion of water for an hour, and then heat until
dissolved. To the hot solution add glycerine to the amount
of 25 per cent, of the glue dissolved. If too thick, add a
little water. The solution may be coloured with aniline
colours if required.
Cements for mounting Photographs. (1) Soak 1 part of
gelatine in cold water for an hour ; take out, and drain off
all the water which will go. Then dissolve in 10 parts
alcohol, and add to the solution 1 part of glycerine.
The cement will keep for an indefinite time, and has only
to be heated when wanted for use. (2) Dissolve 4 parts
of gelatine in 16 parts of hot water. When solution
is completed, stir in 1 part of glycerine. Allow to partly
cool, and then add 14 parts of alcohol. Mix intimately.
(3) Make a solution of 1 part of gelatine in 45 parts of
76 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
hot water, and then add 10 parts of arrowroot which has
been previously mixed with 5 parts of cold water. Boil for
five minutes and then add 10 parts of 95 per cent, alcohol,
together with a few drops of carbolic acid. Stir well until
Jeweller s cement. A cement known as ' Armenian ' cement
is prepared by soaking 8 parts of gelatine in 64 parts of cold
water for twenty-four hours. Then dissolve on the water-
bath and evaporate down to half the bulk, and add to the
concentrated liquor 32 parts of rectified spirit of wine,
straining the whole through muslin. Into this mixture
thoroughly incorporate 4 parts of mastic and 2 parts of
gum ammoniac dissolved in 32 parts of rectified spirit of
Bottle tops. A cement is made by dissolving 5 parts of
gelatine in 5 parts of water, and mixing the solution with
1 part of glycerine.
Leather. A cement for leather is prepared by dissolving
in the cold 8 parts of indiarubber and 4 parts of gutta-
percha in 32 parts of bisulphide of carbon, and then incor-
porating in the mixture a solution of 2 parts of gelatine
dissolved in 2 parts of hot water.
For attaching cloth strips to iron. A powerful cement is
prepared by soaking 100 parts of Cologne glue in cold water
for twelve hours, and then pouring off the water. Place the
softened glue in a clean copper or enamel vessel heated by
steam. During the dissolving, the mass is stirred well with
a wooden spatula. If the glue is too thick, it is thinned with
spirit of wine, but not with water. As soon as the glue solu-
tion has reached the boiling point, 10 parts of boiled linseed
oil are added with constant stirring. When completely in-
corporated, add 10 parts of powdered colophony, shaking
it into mass, and stirring well. In order to increase the
binding qualities of the cement it is well to add 10 parts
LIQUID AND OTHEK GLUES, CEMENTS, ETC. 77
of isinglass, previously cut into narrow strips and dissolved
in 20 parts of spirit of wine, this solution being added to the
boiling glue liquor. The cement is now ready for use. In
the application the iron is warmed and the cement applied
to only so much of the surface as one is able to cover
promptly with cloth strips. The latter are not pressed down
with hand, but with a stiff brush.
Universal cement. This cement is prepared by dissolving in
a flask placed on a water-bath 16 parts of sugar in 48 parts
of water, and adding to the thin syrup 4 parts of slaked
lime. Keep the mixture at a temperature of 70-75* C.
for forty-eight hours, shaking frequently ; then cool and
decant. Dilute 13 parts of this liquor with 13 parts of water,
and in the diluted mixture steep 32 parts of fine gelatine for
three hours before heating, to effect solution. Finally, add
3 parts of glacial acetic acid and 15 drops of carbolic acid.
Glue for belts. To prepare a glue for belts, soak 50 parts
gelatine in an equal weight of water for twelve hours.
Pour off the water and melt the soaked glue on a water-bath.
To the hot solution add 5 parts of glycerine, 10 parts of
turpentine, and 5 parts of boiled linseed oil. Stir well, and
apply while hot.
Glue paste for library use. (1) Mix 6 parts of rice starch
in 48 parts of water, and then add 2 parts of fine glue
previously soaked for twelve hours in 5 parts of water.
Heat over the water-bath until the glue is dissolved. Cool,
and keep in well-stoppered bottles. (2) Mix 12 parts of best
Bermuda arrowroot in 3 parts of water, until a thick cream
is formed, then thin with 10 parts of water, and add 2 parts
of gelatine, previously soaked in 5 parts of water. Boil for
five minutes, then set aside to partly cool, and add 2 parts of
methylated spirit and 6 drops of carbolic acid. Stir well.
Be very particular to add the spirit in a gentle stream.
78 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
The paste is kept in well-stoppered bottles, and is applied
with a brush.
Glue for paper lags. This adhesive is prepared by soaking
100 parts of glue in water for twelve hours. Drain off the
superfluous water and throw the glue on muslin, and manipu-
late so as to get rid of as much moisture as possible, then
melt on a water-bath. Now add 25 parts of glycerine and
5 parts of syrupy glucose, and stir well in. Finally, dissolve
1 part of tannin in the smallest quantity of water possible,
and intimately mix the tannin solution in the glue liquor.
The mixture must be used while hot.
Chromium glue for wood, paper > and cloth. To prepare the
glue : (a) soak 16 parts of white fish glue in 20 parts of water
for twelve hours ; (b) soak 8 parts of gelatine for six hours in 12
parts of water ; (c) dissolve 3 parts of bichromate of potassium
in 6 parts of boiling water. Dissolve (a) and (b) over the
water-bath, and mix the two solutions together ; finally stir
in (c). This glue is exceedingly strong, and if the article
glued be exposed to strong sunlight for an hour, the glue
becomes perfectly waterproof. Of course it is understood
that the exposure to sunlight is to be made after the glue is
thoroughly dry. The one objectionable feature to this glue
is its colour, which is yellow brown. By substituting chrome
alum in place of the bichromate, an olive colour is obtained.
To glue in brass ornaments. The falling-out of ornaments
embedded in wood, where a visible screw is not desirable, is
frequently very troublesome, and a renewed gluing-in rarely
obviates the evil, if it is omitted to dip the metal pieces
previously in weak nitric acid for half a minute.
Such a bath, with subsequent drying, imparts a moderate
roughness to the metallic surfaces which makes the glue take
on much better. The glue employed must be exceedingly
viscous, and never brittle. It is prepared by dissolving 10
parts of glue in 20 parts of hot water, and to the solution is
LIQUID AND OTHER GLUES, CEMENTS, ETC. 79
added a teaspoonful of glycerine and as much of slaked lime,
both ingredients being thoroughly mixed in the glue solution.
It should be applied hot on the slightly warmed pieces, which
should be quickly pressed into the wood. Metal objects
inlaid in this manner never drop out from the wood ; they
can only be torn out by force, on which occasion a thin layer
of the wood is torn away.
Label varnish. The varnished labels of stock vessels often
suffer damage in a very short time from the spilling of the
contents over them, or the dripping after much pouring. To
remedy this inconvenience, a varnish which is unaffected by
the baneful influence of ether, benzene, oil, spirit of wine,
etc., is made and used in the following manner :
Having thoroughly cleaned the surface of the vessel, paste
the label on, and allow to dry well. Then it should be given
a coat of thin collodion to protect the letters from being
dissolved out or caused to run ; then after a few minutes
paint over it a coat of gelatine, prepared by dissolving 5 parts
of gelatine in 25 parts of hot water, being careful to cover in
all the edges. Just before it solidifies, it should be gone
over with a tuft of cotton dipped in a 40 per cent, formalin
solution. It will then soon dry, and become as glossy as
CHAPTEE IX. USES OP GLUE AND GELATINE.
IT has been said that a nation's prosperity may be measured
by its consumption of sulphuric acid. With truth it may
also be remarked that the demand for glue and gelatine is
an evidence of the material progress of a country, for few
industries exist in which one or the other of these products
does not find a use.
One of the most common services to which glue is put is
in the manufacture of matches, this agglutinant, mixed with
chlorate of potash and other chemicals, forming the head or
striking part of every match made. In the great textile
trades a high-grade glue, perfectly sweet and colourless, is
largely used in the dressing and finishing of coloured yarns
and threads, the sizing of worsted and woollen warps, and
the thickening of colours in the printing of fabrics. Many
tons weekly of the same quality of glue are also consumed
in the manufacture of straw hats.
As an adhesive, glue is a necessity in every class of wood-
work, whether it be the manufacture of toys, the making of
household furniture, pianos, organs, billiard tables, veneers,
door panels, picture frames, or, in general, joinery and
carpentry work. When mixed with whiting, white lead,
and sawdust, it forms a cheap composition for moulding
mirror frames, rosettes, etc. Glue is also used in the pro-
USES OF GLUE AND GELATINE. 81
duction of mosaics, plaques, trays, finger-plates, leather wall
coverings, transparent tablets, and in the manufacture of
wallpapers, cardboard boxes, millboards, papier-mache,
emery paper, etc. A large quantity of glue is also used by
shipbuilders and in the Government dockyards and military
arsenals, in the building of battleships and the making of
Cabinetmakers and woodworkers are familiar with the
use of glue in dressing tool cuts and other slight wounds
incident to their calling. The addition of acetic acid to the
glue and a little otto of roses will cover the odour of the glue.
This compound, spread on paper or muslin, makes a good
substitute for adhesive plaster. It is easily and quickly
prepared by placing in a vessel of boiling water a bottle
containing 1 part of glue and 2 parts of water; when
dissolved add 1 part of acetic acid and a few drops of the
perfume. The mixture is kept in a wide-mouthed bottle,
well stoppered by a long cork, which can always be removed
by heating the neck of the bottle. Care should be taken to
keep the mouth of the bottle clean by wiping it with a cloth
dipped in hot water.
Gelatine has an extensive use in culinary and confectionery
work, although its nutritive value is open to great doubt.
So early as 1803 the French Academy, after a lengthy in-
vestigation, reported that though gelatine may partially
replace flesh in soups, yet it could not be taken as a measure
of good value. Many years later (1843) Liebig stated that
gelatine, being a product of the decomposition of albumen,
could not take the place of that body for food purposes, and
this opinion was upheld to a certain extent by Frerichs.
Later, Bischoff, in conjunction with Voit, showed that gelatine
was only of limited value as a heat-producer, instead of fat
and carbohydrates, and that it cannot replace the other
nitrogenous constituents of the body. In one respect only
&2 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
may gelatine claim to have a higher value than albumen,
and that is evidenced in the far less time it takes to digest
the former than the latter.
A jelly for table use is prepared by soaking 10 parts of
gelatine in 8 parts of distilled water for five hours, and then
dissolving on the water-bath. To the gelatinous liquor add
1 part of rectified spirit and 1 part of the white of egg, and
mix well together. Now heat to boiling to completely
coagulate the albumen of the egg, and add 1 part of glycerine,
with a few grains of salicylic acid as a preserving agent.
Mix the whole ingredients together, and filter, while still hot,
through paper moistened with distilled water. The whole
should be kept in a chamber heated by steam while filtering.
In the arts gelatine is largely used for many purposes.
It has been found of service in the formation of moulds for
casting, and one great advantage of the gelatine mould is
that casts without seams can be made from them.
In photography a use is made of gelatine in the numerous
carbon processes introduced by Johnson, Albert, Swan, and
others, in all of which an image is produced by the action of
bichromate of potassium on the gelatine used. This is due
to the oxidising effect of the chromium compound under the
influence of light, which renders the gelatine insoluble in
The advantages of rapidity and fidelity in the copying
of engineering drawings are well known. The widely used
process invented by Poitevin is based on the peculiar property
possessed by a ferric salt of rendering gelatine insoluble so
long as it is not exposed to the actinic rays. The sensitising
solution is composed of 10 parts of ferric chloride and 3 parts
of tartaric acid, both dissolved in 100 parts of water. Before
the paper is coated with the sensitising solution it is floated
on a 6 per cent, solution of gelatine, which is mixed, while
warm, with any suitable pigment of the desired colour. On
USES OF GLUE AND GELATINE. 83
drying the paper it is ready for use. The sensitising and
drying must be carried out in non -actinic light. In using,
the paper is placed behind the tracing or drawing, reversed
as regards right and left. The time of exposure varies
according to the intensity of the light and the thickness of
the paper. The gelatine surface which is not covered by
the lines of the drawing becomes soluble in hot water on
exposure to the light. After the paper is removed from the
printing frame, it should be immersed in water at 80 F.,
when the soluble gelatine will run off the paper.
Few photographers seem to be aware of the immense force
exerted by gelatine in its contraction. The property is,
however, well known to collotypists, often to their cost. If
a collotype plate be overdried, the power of the gelatine is
so great that it tears away the surface of the glass itself,
breaking it up in peculiar fern-like patterns. The surface of
the collotye plate is always ground, and it is that which gives
so firm a hold to the gelatine that the glass is torn away.
It is a curious fact in connection with the matter, that
different grades of gelatine produce a different pattern
fracture. A brittle kind of gelatine yields a different pattern
from that produced by a tough and horny one. Again,
certain salts which are easily crystallised when dissolved in
the gelatine influence the nature of the design. For instance,
a solution of strong gelatine containing 6 per cent, of alum
gave very fine designs, somewhat resembling moss in
appearance, and other salts, such as hyposulphite of soda,
nitrate of potash, and chloride of potassium, will produce
similar forms. This property of gelatine has been taken
advantage of commercially in the manufacture of that kind
of ornamental glass known as ' crystalline glass/ and largely
used for decorative purposes.
In the form of capsules, gelatine is used by druggists to
hold many liquids of a greasy nature castor oil, for instance
84 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
so that they may be swallowed without the unpleasantness
arising from their nauseous taste. The capsules are made by
the aid of a small egg-shaped, highly-polished, little knob of
iron, having a pointed iron stem by which it is held. The
knob is rubbed with a slightly oiled cloth, then dipped in a
warm gelatinous solution, after which the pointed stem is put
into a hole in a board, while the gelatine on the knob is
cooling and hardening. The gelatinous solution usually
consists of 6 parts of gelatine and 1 part of sugar, both being
dissolved in 12 parts of water. In a short time after dipping,
the capsule is cold enough to be removed from the mould,
which is done by cutting the gelatine round the upper part
of the stem with a knife, then pulling off the capsule
dexterously with the fingers. At this stage it should be
elastic enough to pull off without tearing, and to shrink
nearly to the moulded shape directly afterward. A syringe
with a nozzle bent at right angles to the axis of its cylinder
is used to fill it to about three-fourths of its capacity ; if
more were forced in, the gelatinous envelope might possibly
break afterward with changes of temperature. The hole is
closed with a strong solution of gelatine, and the same end
of the capsule is then dipped into a weak solution of gelatine
to give greater security by the thin cap thus applied. The
gelatinous solution used for sealing the capsules always
contains a small proportion of gum. On drying the capsules,
a polished appearance is given to them by rubbing with a
slightly oiled cloth. To protect the capsules from moisture
at the ordinary temperature, they are treated, either before
or after filling, with a weak solution of alum.
Gelatine is one of the many substances used for the coating
of pills, in order that they may not stick together in the box,
and may not be tasted in the act of swallowing them. The
solution used for coating them consists of 1 part of gelatine
dissolved in 2 parts of water. The pills are cleared from any
USES OF GLUE AND GELATINE. 85
dust or powder which may be on their surface, then each pill
is stuck upon the end of a piece of wire, 4 to 5 inches long,
the lower end of the wire being thrust into a basin of sand,
which acts as a kind of pincushion. The pills are next
dipped, one at a time, into the warm solution of gelatine,
then the lower ends of the wires carrying them are replaced
in the sand, standing, while their gelatine-coated knobs are
setting and drying in the air. Sometimes on removing the
pills from the wires a little tube of gelatine from the outside
of the wire comes off with it ; this tube is carefully cut off
with scissors. The hole in the gelatine where the wire
pierced the pill is then closed with a little warm solution of
gelatine, applied by means of a small brush of camel's-hair.
Instead of the customary tin tubes for holding essences,
perfumes, etc., Dr Stohr has introduced tubes made of
gelatine, which, owing to their transparency, allow of control
in the filling. They are said to be cheaper and more durable
than metallic tubes. For contents sensitive to light, coloured
gelatine tubes are employed.
Owing to the increasing scarcity of the natural product,
an artificial ivory is now finding an extensive use, and in the
manufacture, gelatine plays an important part. According
to a recent process based on the employment of those
materials of which natural ivory is composed, consisting as
it does of phosphate and carbonate of calcium, magnesia,
alumina, and gelatine 300 parts of lime are first treated
with sufficient water to convert it into hydrate, but before
it has become completely hydrated or ' slaked,' 75 parts of
an aqueous solution of phosphoric acid is poured on to it,
and while stirring the mixture 16 parts of ground chalk,
2 parts of magnesia, and 5 parts of alumina are incorporated
in small quantities at a time, and lastly, 15 parts of gelatine
dissolved in 20 parts of hot water are added. The point
to aim at is- to obtain a compost sufficiently plastic and as
86 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
intimately mixed as possible. It is then set aside to allow
the phosphoric acid to complete its action on the carbonate
of calcium. The following day, the mixture, while still
plastic, is pressed into the desired form in moulds, and
dried in a current of air at about 150 C. To complete the
preparation of the artificial product, it is kept for three to four
weeks, during which time it becomes perfectly hard. In
another manufacture, that of artificial leather-making,
gelatine is largely consumed. By the process, pure Italian
hemp is cut up very fine, and 1 part of this, along with 1J
parts of coarse cleaned wool, are carded together and formed
into wadding. This wadding is packed in linen and felted
by treatment with hot acid vapours. The resulting product
is washed, dried, and impregnated with a mixture whose
composition varies according to the leather to be produced.
Thus a good sole leather, for instance, is produced in the
following manner : Mix together 50 parts of boiled linseed
oil, 20 parts colophony, 25 parts French turpentine, 10 parts
of glycerine and 10 parts vegetable wax, and heat over a water-
bath with some ammonia water. When the mass has become
homogeneous, add 25 parts of gelatine soaked in an equal
weight of water, as well as a casein solution, made by dissolv-
ing 50 parts of moist, freshly precipitated casein in a saturated
solution of 16 parts borax, and adding 10 parts bichromate
of potassium. The whole mixture is now boiled until it
becomes sticky and the felt is impregnated with it by immer-
sion. The impregnated felt is dried for twenty-four hours at
the ordinary temperature, next laid in a solution of acetate
of alumina, dried, and finally pressed between hot rollers.
Pure Indian ink consists of finely divided carbon cemented
together by certain glutinous juices, gum, gelatine, etc. The
precise nature of the cement or mucilage used by the
Chinese in the manufacture of their inks is not known.
But the greater part of the ink now sold as Indian ink con-
USES OF GLUE AND GELATINE. 87
sists of fine lampblack and gelatine. Pure fine lampblack
is made into a thick paste with a weak solution of gelatine,
containing a few drops of musk, and half as much ambergris,
the paste then being moulded and dried. Most of the
Indian inks met with in commerce possess the disadvantage
that they blot when a damp brush is passed over them, or,
as draughtsmen say, they do not stand. The addition of
alum does little good, but bichromate of potassium accom-
plishes the object by rendering the gelatine insoluble. The
addition does not at all injure the fine shade of colour, as
1 per cent, of it in a very fine powder and intimately mixed
with the ink is sufficient. The bichromate must always be
mixed with the ink in a dry state, otherwise the latter
would lose its friability in water. A drawing which has
been made in artificial light by ink containing bichromate
of potassium must be exposed to sunlight for a few minutes
to render the bichromated gelatine insoluble. In the pre-
paration of roller compositions used by lithographers and
printers, gelatine forms the principal ingredient. As manu-
factured by Hawkins & Stacey, a composition for printers'
rollers is made by soaking 16 parts of gelatine in an equal
weight of water, and then melting over the water-bath.
To the gelatinous solution is gradually added, and then
intimately mixed, 24 parts of linseed oil (warmed to 150 F.).
To the mixture is then added 20 parts molasses and 1 part
dry chloride of calcium, and the whole kept at a temperature
of 90 C. for three hours. If a very tough composition is
required, a mixture of 2 parts resin dissolved by heat in a
little linseed oil, is finally stirred well in the mass. The com-
position may be made non-absorbent of water, by dispensing
with chloride of calcium, and substituting a similar amount of
carbonate of bismuth.
In the manufacture of artificial silk under the patents
worked by the Vanduara Silk Company, the filaments are
88 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
composed entirely of gelatine, specially prepared for the
purpose, and forced by strong pressure through fine nipples.
The threads are capable of taking on any shade of colour,
by immersion in the dye-bath.
In the textile trades, and also in the finishing of white
straw hats, considerable quantities of gelatine are used ;
while in the manufacture of the finer classes of paper it is
used as a size. As a substitute for wax, gelatine finds a use
in covering the corks and upper part of the necks of bottles.
CHAPTEK X. RESIDUAL PRODUCTS FROM
GLUE AND GELATINE.
ALL crops contain certain mineral matters in their ashes.
These substances are absorbed from the soil during the
growth of the plants. Hence no land can produce crops
without deterioration in their fertilising power. To main-
tain the fertility of the soil by returning to it these
ingredients which former crops have exhausted as food,
recourse is had to natural or artificial manures which return
to the land the necessary phosphates, nitrogen, and potash
for the production of vegetable structure. To enrich the
soil of this country over 32,000,000 pounds sterling are
annually spent in fertilisers, and of this vast sum fully one-
sixth is derived from the residual products of the glue and
gelatine industry. These products will now be described,
along with the uses to which they are put.
Skin Residues. The residual matters left in the digestion
of skins are limited in quantity. They contain no phosphate
of lime, and are only of value from the small proportion of
gelatinous matter left unexhausted in the vats. They contain
nitrogen equivalent to about 3 per cent, of ammonia, and
are only of service, when dried, in mixing with bone or
mineral superphosphates in the manufacture of nitrogenous
manures, for wheat, turnips, hops, etc. The drying is
90 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
carried out in a jacketed cylinder horizontally supported
by two pedestals ; the cylinder has a length of 14 feet and
a width of 6 feet. Eunning the length of the cylinder is a
shaft to which are affixed a number of beaters which stir up
the mass and equally expose the whole to the heat of the
jacket. The steam supplying the jacket is superheated by
passing it through a number of coils heated by the waste
heat of the steam boiler. After five to six hours' exposure
to a temperature of about 400 C., the mass in a dry and
friable condition is withdrawn through a door placed at the
end of the cylinder, and is ready for mixing in the manure
Fish Residues. Fish residues, after the extraction of
the oil and gelatinous matters, and when dried in the jacketed
cylinder, are used as a phosphatic nitrogenous manure for
cereal and root crops and in floricultural work, especially
for roses, chrysanthemums, primulas, cyclamens, and other
flowering plants. The necessary potash, as sulphate, is added
during the passage of the dried residues through a disinte-
grator. The finished manure contains
Per cent. Per cent.
Nitrogen, equal to ammonia, . 3'69 3'36
Phosphates (fish-bone), . . 914 871
Potash (sulphate), . . . 6'25 6'04
The manurial value of dried fish residues is much increased
by mixing them with high-grade bone superphosphates of
ammonia and potash, yielding a manure containing
Soluble phosphates, . . . 12 to 14
Insoluble . . 14 to 16
Ammonia (partly soluble), . . 8 to 10
Potash (as sulphate), . . . 6 to 8
From certain species of fish, the skins are prepared and
manufactured into an interesting variety of articles. By
RESIDUAL PRODUCTS FROM GLUE AND GELATINE.
means of numerous complicated processes they are manipu-
lated until they resemble, and would easily be taken for,
leather, although of a more glutinous and pliable nature.
In one speciality this strange substance is cut into long thin
strips and plaited very closely together for whiplashes, and
to cover portions of the handles of more expensive whips.
Certain kinds of lashes and harness laces are also made from
such skins, combining flexibility and toughness.
Bone Residues. In a degreased and degelatinised form
the residual bones hold an important place in the works' pro-
duction. When air-dried, the following analyses represent
their composition, as made by the author :
In parts per 100.
Organic matter, ....
Phosphate of lime, ....
Carbonate of lime and magnesium, .
Oxide of iron, .....
Alkaline salts, ....
Equal to ammonia, ....
Degreased and degelatinised bones are used on the land,
either ground to a meal or crushed to a quarter-inch size by
a mill. When treated with sulphuric acid, which renders a
portion of the phosphate soluble and thus more readily
taken up by the growing crops, they form superphosphates.
When used alone or in conjunction with mineral superphos-
phates, they form the basis of special or mixed manures.
92 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
Degreased and degelatinised bones naturally contain less
nitrogen than raw bones, and consequently are of less value
agriculturally, owing to this deficiency. On the other hand,
the phosphates are increased and in a condition more readily
decomposed in the soil.
They are specially suitable where early results are required.
When ground to a meal, the bones are liable to adul-
teration, which remains undetected unless by analysis ;
gypsum and the sweepings from granaries are used for the
The following analysis by Dr Voelcker shows the low
manurial value of a meal adulterated with sulphate of lime
In parts per 100.
Organic matter with salts of ammonia, 14'40
Phosphate of lime, magnesia, etc., . 4CK32
Sulphate of lime, . . . . 3542
Alkaline salts, and carbonate of lime, 4'21
Siliceous matter, . . . . 1-70
Bone superphosphate. Calcium unites with phosphoric acid,
forming three distinct compounds, viz. :
(a) Mono-calcium phosphate (CaH 4 P 2 8 )
(5) Bi-calcium phosphate (Ca 2 H 2 P 2 8 )
(c) Tri-calcium phosphate (Ca 3 P 2 8 ).
If tri-calcium phosphate, which is an insoluble salt, is
acted upon by a combining proportion of sulphuric acid, it
is converted into mono-calcium phosphate, the soluble form
of phosphate required by the manure-maker. With the
discovery of this action by Justus von Liebig originates the
well-known superphosphate industry.
RESIDUAL PRODUCTS FROM GLUE AND GELATINE. 93
The change is represented by the equation :
Tri-calcium Sulphuric Sulphate Mono-calcium
Phosphate. Acid. of Lime. Phosphate.
Ca 3 P 2 8 + 2(H 2 S0 4 ) - 2(CaS0 4 ) + CaH 4 P 2 8
310 196 272 234
From the combining proportions it is seen that 310 parts
of insoluble phosphate require for conversion 196 parts of
sulphuric acid and yield 234 parts of soluble phosphate
mixed with 272 parts of sulphate of lime (gypsum). Sup-
posing that the mineral matter of bones was composed
entirely of tri-calcium phosphate, then each cwt. would
require for conversion into superphosphate of lime (CaH 4 P 2 8
+ 2CaS0 4 ) 0-6322 cwt. of sulphuric acid, the superphosphate
containing 53'75 per cent, of mono-calcium phosphate.
These results are never obtained in practical working,
owing, in the first instance, to the amount of tri-calcium
phosphate in the bones, and secondly, to secure the necessary
mechanical condition, only a portion and not the whole of
the insoluble phosphate is acted upon, the sulphuric acid
being adjusted to effect this purpose. A too perfectly dis-
solved manure would be damp and pasty, and unworkable in
the drills. The presence of carbonate of lime in the bones
is of mechanical advantage, insomuch that it renders the
superphosphate light and spongy, owing to the carbonic
acid liberated during the action.
The following analyses by the author represent the com-
position of bone superphosphates :
In parts per 100.
Moisture, .... 14-26 15-51
Organic matter, . . . 10-39 ll'S4
Mono-calcium phosphate, . 21*35 19'66
( = Tri-calcium phosphate made
soluble), .... (28-26) (26'02)
Carry forward, . . 46'00 47'01
94 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
In parts per 100.
Brought forward, . . 46*00 47'01
Insoluble or tri-calcium phosphate, 6*48 915
Sulphate of iron, . . . trace 08
Sulphate of lime, . . . 42'08 38'53
Sulphate of magnesia, . . 2'35 2"58
Alkaline salts, . . . . 211 144
Insoluble matter (silica) . . 0'93 1-21
Bone superphosphate may be made in a small way by
mixing in a shallow wooden trough 6 cwt. ground de-
gelatinised bones with one-third their weight of water, and
then cautiously adding to the mixture 3 cwts. of brown
vitrol (BOV) or 2 cwt. of white vitrol (wov). Mix thoroughly,
and then shovel into a heap, and allow to ' set ' for two days.
Break up the lumps, pass the whole through a riddle, and
finally bag the finished manure.
In working on a large scale, the degelatinised bones, alone,
or with a proportion of mineral phosphates, are first crushed
and then ground to a fine powder in a mill, raised by an
elevator to the dissolving floor of the manure house, and
fed into a mixer for treatment with sulphuric acid. The
mixer may be of the Morrison type, which is cylindrical in
form, the bottom being circular, while the sides are splayed
outwards to give good ' boiling up ' room. It is built of cast
iron flanged plates bolted together, and has a wooden top
to which are fixed the acid-supplying pipe, the hopper for
charging, and the exit flue for carrying off the gases generated
during the mixing. The mixture of phosphates and acid
is stirred by a number of cast iron ' beaters ' fixed on to a
shaft in a spiral form, so that the charge may be forced,
when finished, to a discharging door, from whence it falls
into a ' den ' or brick chamber beneath. In some manure
works the mixer is fixed horizontally, and consists of a lead-
RESIDUAL PRODUCTS PROM GLUE AND GELATINE. 95
lined wooden trough, bevelled at the top, the charging door
being part of the bevel. The trough is fed with sulphuric acid
from an overhead tank, which is provided with a gauge-glass
and scale divided into inches, each inch representing a
certain weight of acid and is well mixed witli a charge of
8 to 9 cwts. of degelatinised bones for five minutes, by a
spiral arrangement fixed on to a shaft running the length of
the trough. At one end of the mixer is placed the discharging
door, through which the hot and soft mass is then forced to
a brick chamber underneath for cooling and setting. The
gases generated during the mixing consist of carbonic acid,
with smaller proportions of hydrofluoric and hydrochloric
acids intermingled with steam, are carried off by an outlet
pipe to a series of flues so arranged with a view to cooling
the gases and lowering the tension vapour. On cooling, the
steam condenses in the form of moisture, and thus carries
down with it the soluble acid gases. In the manufacture
of superphosphates the consumption of sulphuric acid
depends on the nature and amount of impurities in the raw
material used. With mineral phosphates, the impurities,
which range from 10 to 20 per cent., consist of carbonate
and fluoride of calcium, alumina, and oxide of iron, and
require to be neutralised with acid over and above the
amount necessary to convert the tri-calcium phosphate into
the soluble mono-calcic salt. That this amount is consider-
able may be seen from the following table, showing the
absorption of acid per cwt. of each individual impurity
1 cwt. carbonate of lime requires 1*225 cwt. sulphuric
acid to form sulphate of lime (CaS0 4 ).
1 cwt. alumina requires 2'854 cwts. sulphuric acid to form
sulphate of alumina (A1 2 3S0 4 .8H 2 O).
1 cwt. oxide of iron requires 1'8375 cwt. sulphuric acid to
form sulphate of iron (Fe 2 3S0 4 ).
96 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
1 cwt. fluoride of calcium requires 1*256 cwt. sulphuric
acid to form hydrofluoric acid (HF).
In bone phosphates (degelatinised bones) the only appre-
ciable impurity is the carbonate of lime, which varies from
6 to 8 per cent. , consequently the acid consumed for their
conversion would be less than in the decomposition of
Sulphuric acid is manufactured in varying strengths, and is
sold to the manure-maker either at a price per ton of given
strength or so much per unit or degree as registered by the
Twaddell hydrometer at a temperature of 60 F.
The acid found most suitable for dissolving degelatinised
bones is the quality known as ' chamber acid/ having a
specific gravity of 1*57, equal to a Twaddell strength of 114,
and containing 66 per cent, pure sulphuric acid. With a
charge of 9 cwts. of bones and 7 cwts. of acid, renewed every
ten minutes, a mixer will produce 30 tons of superphosphates
daily, which are ready for removal from the chambers two
of which are necessary for the working of each mixer
every alternate day.
Well-made bone superphosphates are friable and porous,
and consist mainly of soluble and insoluble phosphates with
sulphate of calcium, thus supplying the land with lime,
phosphoric, and sulphuric acids. When kept for a lengthy
period before using, the percentage of soluble phosphate
gradually decreases, owing to the formation of bi-calcium
phosphate by the action of the insoluble phosphate. This
change is represented by the following equation :
Tri-calciura Mono-calcium Bi-calcium
phosphate. phosphate. phosphate.
Ca 3 P 2 8 + CaH 4 P 2 8 = 2Ca 2 H 2 P 2 8
(Insoluble) (Soluble) (Slightly soluble)
The formation of bi-calcium phosphate, which may amount
to 3 or 4 per cent, in the space of a few months, is a distinct
KESIDUAL PRODUCTS FROM GLUE AND GELATINE. 97
loss to the soluble power of a superphosphate, for, owing to
its slight solubility, it is but slowly diffused through the soil.
Bone superphosphates are brought into the market con-
taining soluble phosphates ranging from 20 to 26 per cent,
tri-calcium phosphate, rendered soluble, the insoluble varying
from 6 to 12 per cent.
A small proportion of nitrogen is also present, derived
from unexhausted nitrogenous matter left in the degelatinised
When mixed with a small proportion of sulphate of
ammonia, bone superphosphates are sold under the name of
' dissolved bones/ containing
Soluble phosphate, . . . . 20 to 22
Insoluble, 10 to 12
Nitrogen, equivalent to ammonia, . 3 to 4
' Dissolved bone compound ' is a superphosphate of lower
strength than ' dissolved bones, ' and contains
Soluble phosphate, . . . . 16 to 18
Insoluble .... 7 to 9
Nitrogen, equivalent to ammonia, . 2 to 3
As a substitute for Peruvian guano, bone superphosphates
mixed with sulphate of ammonia contain the following :
Soluble phosphate, . . . . 14 to 16
Insoluble ; , .... 6 to 8
Nitrogen, equivalent to ammonia, . 12 to 13
Probably there is no phosphatic manure which deserves so
much praise by the farmer as bone superphosphate, and if he
wishes to keep abreast of the times and is anxious to grow
two blades of grass where only one grew before, to carry a
larger head of stock and of better quality, to market more
fat cattle, and to produce more milk and of higher standard
98 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
quality, he must use high-class superphosphate largely and
Nearly all soils are deficient in phosphoric acid, but that
deficiency can be supplied in the form of superphosphate,
the cheapest source in its most soluble and effective form,
and it can be applied with marked advantage to all cultivated
crops. Land kept under pasture and grazed with farm stock
for a series of years becomes steadily poorer in phosphoric
acid (phosphates), because it is carried away in the bones
and carcases of animals grazing on it. Pastures where ewe
flocks are kept and lambs reared lose much phosphates in the
bodies of the young animals, all of which have been taken
from the soil ; milch cows also carry off large quantities of
phosphates in their milk, which contains much of this
essential material, while the bones of all young cattle and
horses are formed at the expense of phosphoric acid in the
soil. Here again superphosphate comes to the rescue, and
the effects produced by applications of it are marvellous.
These results are seen in the experiments made by Mr Alex.
Burr, a leading agriculturist, for the purpose of testing the
action of several different manures. He divided two fields
of 40 acres each of black stony loam land that had been laid
down to grass for two years into four sections, manured with
the following :
Section. Manure per acre. Yield per acre.
1, . . No manure, . . .10 cwt. hay.
2, . . Kainite, 5 cwt., . 15
3, . . Basic slag, 5 cwt., . . 15
4, . . Superphosphates, 5 cwt., . 19
In the following year (1900) the same sections (Nos. 2, 3,
and 4) were treated as below :
Section. Manure per acre. Yield per acre.
2, . . Kainite, 5 cwt., . . 28 cwt. hay.
. . Nitrate of soda, 1 cwt., . 28^
RESIDUAL PEODUCTS FROM GLUE AND GELATINE. 99
Section. Manure per acre. Yield per acre.
3, . . Basic slag, 5 cwt., . . 27 cwt. hay.
. . Nitrate of soda, 1 cwt., . 27
4, . . Superphosphate, 5 cwt., . 34 ,.
. . Nitrate of soda, 1 cwt., . 34
The same authority also shows the milk yield of cows,
by manuring with superphosphate. In 1899, 150 acres of
unmanured meadowland carried 40 cows, yielding 14,400
gallons of milk at 6d. per gallon. In 1901 the same meadow-
land, after a top-dressing of superphosphate, carried 60 cows,
yielding 36,000 gallons of milk at 7d. per gallon, an increase
of 685 in the production of milk alone. It will be seen
that not only was the quantity of milk increased, but also
the quality, as shown by the rise in price and as certified by
analysis. A large proportion of superphosphates, whether of
bone or mineral origin, is converted into mixed or special
manures for certain crops. A mixed manure is not a
chemical combination, but a mechanical mixture of certain
ingredients required by any particular crop for nutritive
purposes. For instance, oats, wheat, rye, and other plants
thrive principally on nitrogen obtained from sulphate of
ammonia, nitrate of soda, or nitrogenous organic matter, such
as dissolved wool, woollen refuse and shoddy, fish refuse,
leather-meal, etc. With potatoes, clover, beans, etc., potash is
the dominant nutritive agent, and this is supplied as chloride,
sulphate, or in the form of kainite containing 23 to 25 per cent,
of sulphate of potash ; while grass, maize, turnips, and other
crops depend on phosphates principally, with minor propor-
tions of nitrogen and potash. Thus knowing the require-
ments of each particular crop, the manufacturer is able to
compound a suitable manure of any desired strength and
Manure makers manufacturing their own superphosphate
add the required weight of ingredients to the mass removed
100 GLUE, GELATINE, AND THEIR ALLIED PKODUCTS.
from the ' den ' or chamber, and pass the whole through a
disintegrator to break any lumps and reduce to a powder.
Manufacturers in a small way of business buy the super-
phosphate at a price per unit of phosphoric acid made
soluble, then add the calculated amounts of nitrogen and
potash, and well mix the mass together by turning over two
or three times.
The following are special bone manures, made from
degreased and degelatinised bones, mixed with 25 per cent,
of mineral superphosphate, made from Algerian raw phos-
phates ; each manufacturer has his own standard of strength,
and sells at a price accordingly.
(a) Turnip manure.
Soluble phosphates, . . . . 17 to 20
Insoluble . . . . 8 to 12
Nitrogen, equivalent to ammonia,- . 2 to 3
Potash, equivalent to sulphate of potash, 3 to 4
The following mixing forms an excellent manure for turnips
and mangels :
Bone superphosphates (20 per cent, soluble), 10 cwt.
Kainite (24 per cent, sulphate of potash), . 2 ,,
Sulphate of ammonium, . . . 2
Common salt, . . . . . 6 ,,
5 to 6 cwt. of the manure applied per acre.
(b) Potato manure.
Soluble phosphates, . . . . 18 to 20
Insoluble .... 6 to 8
Sulphate of potash, . . . . 7 to 9
Nitrogen, equivalent to ammonia, . 3 to 4
A mixing for potato manure consists of
Bone superphosphates (20 per cent, soluble), 12 cwt.
Kainite (24 per cent sulphate of potash), . 6
Sulphate of ammonium, . . . . 4
5 to 6 cwt. applied per acre.
RESIDUAL PRODUCTS FROM XHJJS. AND jQELATtNE.
Another mixing is made from
Degreased and degelatinised bones, . 1J cwfc.
Algerian phosphate, . . . . 1
Leather waste, J
Shoddy (8 per cent, nitrogen), . . 1
Shoddy (5 )..!
Sulphuric acid, 110 Tw., . . . 2f
Of this mixture 14 cwt. are taken and mixed with
Dried flesh, 4J cwt.
Sulphate of ammonia, . . . 1
Sulphate of potash, . . . . f
The mass is then passed through a disintegrator. High-class
potato manure is made from
Degreased and degelatinised bones, . 1J cwt.
Florida phosphate, ^
Leather waste, 2
Shoddy (15 per cent, nitrogen), . . J
Sulphuric acid, 110 Tw., . . 2|
Of this mixture 15 cwt. are taken and mixed with
Dried flesh, 2 cwt.
Sulphate of ammonia, . . . . 2
Sulphate of potash, . . . . J
Sud cake (2 per cent, of nitrogen), . . 1
4 to 5 cwt. of the mass is applied per acre.
(c) Special manure for grass lands.
Soluble phosphates, . . . . 14 to 18
Insoluble . . . . 4 to 8
Nitrogen, equivalent to ammonia, . . 3 to 4
(d) Special manures for cereal crops.
(1) Wheat manure.
Soluble phosphates, . . . . 16 to 18
Insoluble . . . . 4 to 6
Nitrogen, equivalent to ammonia, . . 4
Applied 4 to 5 cwt. per acre.
102 GLUE, GfcLATINE, AND THEIK ALLIED PRODUCTS.
The following mixing has been used with great success by
Lawes and Gilbert : =
Sulphate of potash, .... 200 Ibs.
Sulphate of ammonia, .... 200
Sulphate of soda, 100
Sulphate of magnesia, . . . 100
Bone superphosphates, .... 400
(2) Barley and oat manure.
Soluble phosphates, . . . . 18 to 20
Insoluble .... 5 to 7
Nitrogen, equivalent to ammonia, . 3^
(c) Pea, bean, and vetch manure.
Soluble phosphates, . . . . 20 to 22
Insoluble . . . . 3 to 4
Nitrogen, equivalent to ammonia, . 3^ to 4^
The quantities used are 4 to 5 cwt. per acre.
(/) Sugar-cane manure.
Soluble phosphates, 20
Sulphate of potash, 9
Nitrogen, equivalent to ammonia, . . 11
Applied 5 cwt. per acre.
(g) Special celery and onion manure contains :
Soluble phosphates, . . . 14 to 16
Insoluble . . . . 4 to 6
Sulphate of potash, . . . . 3 J to 4
Nitrogen equivalent to ammonia, . 3 to 4J
(h) A well-balanced and all-round fertiliser, suitable for
all kinds of crops, especially mangolds, turnips, swedes, and
mustard, contains the following :
RESIDUAL PEODUCTS FROM GLUE AND GELATINE. 103
Soluble phosphates, . . . . ,16
Nitrogen, equivalent to ammonia, ... 2
(*) For all root crops, a useful manure is made by treating
degreased and degelatinised bones with sulphuric acid and
then mixing with the dried offal from lairages. In a manure
of this character the nitrogen is derived from organic and
animal matter, and delivers up its store of plant food in a
slower manner than when the nitrogen exists in the form of
sulphate of ammonia or nitrate of soda, both highly soluble
salts, which are liable, when applied, to be washed down
into the drains in wet weather. A cheap and yet effective
manure of this character contains
Soluble phosphates, . . . . 10 to 12
Insoluble . . . . 3 to 4
Sulphate of potash, . . . J to 1
Nitrogen, equivalent to ammonia, . 2 to 3
Recovery of Phosphate of Lime. In the manufacture
of gelatine the degreased bones are steeped in a dilute
solution of hydrochloric acid, which dissolves out practically
the whole of the phosphate of lime of the bones, and the
recovery of this substance forms a very important item in
the economical working of the factory. To effect this
recovery the acid liquors and wash waters are passed through
a filter to remove any suspended matter and then run into a
number of precipitating vats, and treated with a neutralising
base, such as lime in the form of milk of lime, chalk made
into a cream, or a solution of calcium sulphydrate, the base
being added until the solution is slightly alkaline. If the
addition of the neutralising base is stopped while the solution
is still acid, the precipitate consists chiefly of bi-calcium
phosphate. When the precipitation is completed, the tri-
104 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
calcium phosphate, as a white ' sludge,' falls to the bottom ;
and after washing three or four times with cold water, the
washed ' sludge ' is pumped to large presses, whence it is freed
from a large portion of the water, the cakes inside the
filtering chambers retaining only about 10 per cent. On
removing the filter plates, which are mounted on deep
rectangular bars, the cakes fall on to a travelling band which
carries them to a drying room, where they are dried in
shallow earthen dishes arranged on racks, the heat being
supplied by flues running the length of the room.
Precipitated phosphate forms a valuable manure, and is
most suitable for light, sandy soils. As tri-calcium phosphate
it is far more soluble in water than the finest ground mineral
Precipitated phosphate is also largely used in the manu-
facture of a substitute for cream of tartar in baking. For
this purpose it is ground to a fine state of division, and
mixed with sulphuric and phosphoric acid in the following
Precipitated phosphate, . . . .112 Ibs.
Sulphuric acid, 91
Phosphoric acid, 42
The pasty mass thus formed is dried by steam heat, ground
again to a fine powder, passed through a 60-mesh screen,
and then intimately mixed with flour or farina in proportions
necessary for the strength of acidity required.
Bone Ash. After degreasing and degelatinising white
bones, the bye-product, when completely burned in a retort
or kiln, forms a white-coloured ash, which in its concentrated
state contains 75 to 85 per cent, of bone phosphate existing
as tri-calcium phosphate. The ash, of which large quantities
are imported from South America, is used in the manufacture
of high-strength superphosphates. The following analyses
RESIDUAL PRODUCTS FROM GLUE AND GELATINE. 105
by the author represent the composition of pure and com-
mercial samples of bone-ash :
In parts per 100.
Pure bone Commercial
ash. bone ash.
Unconsumed carbon, ... '29 2*92
Tri-calcium phosphate, . . 85'89 72*66
Lime, 515 711
Magnesia, 3'64 3'39
Oxide of iron, .... trace '35
Carbonic acid, .... 1'58 1'72
Alkaline salts, . . . . 1'39 1-69
Silica, 2-03 6*97
Dissolved bone ash or bone ash superphosphate is prepared
in the same way as bone superphosphate, and when well
made it should be in a fine, dry, powdery condition. From
the high percentage of soluble phosphate, dissolved bone ash
forms a valuable manure when applied to cereals and root
crops on cold clayey soils.
The following is an analysis by the author of dissolved
In parts per 100.
Unconsumed carbon, 2*62
Mono-calcium phosphate, . . . 2918
= tri-calcium phosphate rendered soluble (38 - 65)
Insoluble or tri-calcium phosphate, . . 316
Sulphates of lime and magnesia, . . 44'47
Alkaline salts, 1*07
Leather Waste. As previously remarked, leather waste
is not used in the manufacture of glue, owing to the want of
106 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
a practical method to dissociate the tannin from the gelatine,
and leave the latter in a condition available for the glue
manufacturer. It is, however, important as a material, rich
in nitrogen, to the manure-maker. To make leather into a
nitrogenised manure, it is first roasted and then ground to a
fine powder in a mill, and afterward treated with superheated
steam, which removes the greater part of the tannic acid.
On drying it in a jacketed pan, and then passing it through
a disintegrator, a meal is produced which, without further
treatment, is used by the farmer as a manure.
Leather meal contains a high percentage of nitrogen ; this
product, however, being in an insoluble form, is not so
readily available for plant food as the nitrogen in sulphate of
ammonia, nitrate of soda, or in chemically treated leather.
Waste leather to be made available as a quick manure is
best treated along with shoddy and raw ground phosphates,
with sulphuric acid in the superphosphate mixer, in the
following proportions :
Leather waste, 2 cwt.
Florida phosphates, .... 2
Shoddy (containing 15 per cent, nitrogen), J
Sulphuric acid, 110 Tw., 2
The mixture, which contains nitrogen equal to 2 J per cent, of
ammonia, forms a base in the compounding of manures for
cereal or root crops.
Leather waste is also used in the manufacture of artificial
leather, leather boards, etc. For these purposes, the waste
is first steeped in weak lime water, and then ground to a
fine powder in a rag engine as used by papermakers. The
ground leather is then mixed with about half its weight of
good Manila rope, coloured with Venetian red, and is now
ready to be made into either leather board or stiffenings for
heels and toes of boots and shoes. In another method of
RESIDUAL PRODUCTS FROM GLUE AND GELATINE. 107
treatment leather scrap is shredded and then mixed with a
strong solution of ammonia, which forms a gelatinous mass.
It is soluble in water, and has no elasticity until it is mixed
with indiarubber dissolved in bisulphide of carbon and well
kneaded, when it is rendered waterproof. The kneaded mass
is then pressed into moulds.
The use of leather board in the manufacture of boots and
shoes is one of the bad features of the business. One kind is
used for lapping and for veneering laps. The material is
made to look like leather and cut like leather. A thin split
of true leather makes a veneer that satisfies the demands of
the buffing machine. The best board is made from scrap
leather mixed with jute, and is used for counters, heel
stiffenings or box toes. When properly treated and manu-
factured, these counters do good service. When leather
board is backed with a leather split and moulded into a
stiffening, the product is a union counter. Leather board is
also used in the making of chair seats, table tops, etc.
CHAPTER XL ANALYSES OF THE RAW
AND FINISHED PRODUCTS.
THE chemical laboratory fulfils a very important function
in the successful conducting of a large works, and as a guide
to the chemist in charge this chapter is devoted to a descrip-
tion of the methods adopted in making the many analyses
required of the raw and finished products. The raw materials
entering the works may be divided into two classes hide
pieces and rough bones. With the former the examination
is solely confined to their glue-yielding capacity, and this
is best carried out by making a boiling, under conditions
closely approximating to the work on a large scale, with an
average sample in a small experimental glue plant, which is
an important feature in a well-equipped laboratory, and
testing the jelly formed on cooling the liquor by the shot
test for tenacity.
Assuming that all the nitrogen present is of a glue-forming
nature, this may be estimated by Kjeldahl's process as given
below ; the result multipled by 5*4 indicates the amount of
Raw Bones. Although raw bones are not bought under
a guarantee, yet it is advisable to examine each day's delivery
for moisture, fatty matter, and nitrogen, and this is made as
follows, from a carefully selected and crushed sample :
ANALYSES OF THE RAW AND FINISHED PRODUCTS. 109
(a} Moisture. Five grams are weighed out into a porcelain
crucible and heated for twelve hours at a temperature of
100 to 105 G. On cooling under the desiccator and re-
weighing, the loss of weight represents the moisture.
(&) Fat. The fat is estimated by a Soxhlet's extraction
apparatus as seen in fig. 25, which consists of a small flask
A, extractor B, condenser C. The
tube holding the sample has a small
opening at the bottom, which is
covered with asbestos to prevent
any loss of the sample. Before
inserting in the extractor, the tube,
which must be perfectly dry, is
weighed and then three parts filled
with the sample. On re-weighing,
the difference in weight represents
the amount taken. The flask A,
which must be thoroughly dry, is
weighed and the weight noted. In
working the apparatus, the solvent
ether is poured in at the top of
the condenser until the flask A is
about half full, and heat applied to
the vessel of water in which the
flask is placed. Owing to the boil-
ing point of ether, distillation
quickly commences, the low ether FIG. 25. Soxhlet's apparatus,
vapours passing up through one
of the limbs of the extractor into the condenser, and on
condensation trickle down on to the bones within the tube,
dissolving out the fatty matter. When the syphon over-
flow is reached, the ether with the fat it has dissolved is
syphoned off into the flask below, the ether being again
driven off, leaving the fat behind. This is repeated some
110 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
six times, when it may be safely assumed that the bones are
denuded of their fat. The flask A is now disconnected, and
after wiping is placed in the air-bath and heated for twelve
hours at a temperature not exceeding 105 C., this being
necessary to drive off any moisture passing over with the
ether to the flask. On re-weighing the flask, which is coated
with a film of fat, the difference in weight represents the
amount of fat in the sample taken. The tube also on removal
may be dried for twelve hours at a temperature of 100
to 105 C., and re-weighed ; the loss in weight represents the
fat and moisture, from which the percentage of the former
can be readily calculated.
(c) Nitrogen. This is estimated by Kjeldahl's process,
which is based on the oxidation of the organic matter, the
nitrogen being converted into ammonia, which is fixed by
the sulphuric acid present forming sulphate of ammonia,
this salt being subsequently decomposed by a solution of
caustic soda, and the liberated ammoniacal vapours being
absorbed by a standard solution of sulphuric acid. The
oxidation is effected in a Jena flask, into which 5 grams of
the sample are placed and then covered with 20 c.c. of con-
centrated sulphuric acid, along with 10 grams of fused
bisulphate of potash. The flask is heated on a sand-bath,
at first gradually, and as the oxidation proceeds, strongly, for
about three hours, when the liquor will have assumed a
clear, pale yellow appearance, which indicates the end of the
action. On removal of the flask from the sand-bath, it is
cooled, and then cautiously filled to the neck with water,
stirring well after each addition. The contents of the flask
are now washed into a large flask, from which a tube dips
under a layer of standard sulphuric acid contained in a small
flask kept cool by a stream of water. Connected with the
large flask is a funnel with stopcock for conveying a solution
of caustic soda, and on applying heat with the Bunsen flame
ANALYSES OF THE RAW AND FINISHED PRODUCTS. Ill
the ammonia is distilled over and is absorbed by the standard
acid. On boiling for an hour, the small receiving flask is
disconnected, and the excess of acid remaining is titrated
with standard soda solution. Both the acid and soda solu-
tions are of deci-normal strength. From the number of c.cs.
of acid uncombined with ammonia is calculated the per-
centage amount of nitrogen, and this multiplied by 5*4 gives
the percentage yield of glue.
Benzene. In the degreasing of the bones the benzene
solvent should be frequently tested so that any diminution
in strength may be noted. The testing is carried out by
fractionation, and the sample should closely approach the
Boiling point, 100 0.
Below 100 C. . . . Nothing
100 to 104 . . . 14 per cent.
104 to 110 . . . 20-5
110 to 115 ... 38
115 to 121 . . . 16-5
121 to 126 ... 6
126 to 132 ... 4
132 to 138 ... 1
Over 138 . . . Nothing
Condensed Water. In running the fat from the benzene
plant, the condensed water is daily tested for any loss of
gelatinous matter during the degreasing, and the amount, if
any, is estimated by the Kjeldahl process.
Decreased Bones. The degreased bones may retain a
portion of fat unextracted during the benzene treatment.
This is estimated by the Soxhlet apparatus, as described at
p. 109. The loss should not exceed 5 per cent.
Refined Fat. Refined fat is sold on a basis of 98 per cent.
The impurities generally accompanying the pure fat are
(1) moisture ; (2) naphtha ; (3) mineral matter ; (4) organic
matter other than fat. They are estimated as follows :
112 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
(a) Moisture. Determined as in (a) under the heading of
' Raw Bones.'
(b) Naphtha. 100 grams of the fat are weighed out and
filled into a flask fitted with a cork perforated with three
holes. Through one is fixed a thermometer dipping down
into the fat Through the second a tube is passed which is
in connection with a second flask generating steam, the
junction between the two being closed by a clip. Through
the third opening a bent tube connected to a Liebig's
condenser is passed. To the other end of the condenser is
fixed, with rubber tubing, a bent tube dipping under water
contained in a flask having a long neck and graduated into
^o c.cs. The flask containing the fat is partly embedded in
sand on a sand-bath, and is heated with a Bunsen burner
underneath. The heat is raised to about 160 C., which
drives over the larger portion of the naphtha present, while
the remainder is dispelled by the current of steam which is
allowed to play on the fat for half an hour. The vapours are
condensed in their passage through the condenser to the
receiving flask, and in the latter will be found any naphtha
present, floating as a thin film on the surface of the water.
On disconnecting the flask and filling with tepid water to
about half-way up the neck, then cooling to the normal
temperature, the naphtha may be read off in fractions of
a c.c. , which, when multiplied by the specific gravity, shows
the percentage amount present.
(c) Mineral Matter (Ash). Into a crucible of constant
weight 1 gram of the sample is weighed and then slowly
incinerated to a black mass. The crucible is now removed
to a muffle and heated to redness for ten hours, then cooled
under the desiccator, and re- weighed. The increase of weight
represents the mineral matter present in 1 gram of the
sample ; on multiplying by 100 the percentage amount is
ANALYSES OF THE RAW AND FINISHED PRODUCTS. 113
(d) Organic Matt er other than Fat. This is estimated by
treating 2 grams of the sample with ether, stirring well and
pouring on to a tared filter, then washing the residue with
the same solvent until no trace of fat is visible, when a few
drops are evaporated on a watch-glass. The tared filter
paper on drying at 100 C. for five hours is re- weighed, and
the increase in weight represents the organic matter other
than fat in the 2 grams taken.
Glue. In judging the value of glue many users rely on the
colour, smell, and shrinkage. These qualities alone are not
a safe guide in forming an opinion, for a glue may have good
colour, be free from smell, and well shrunken in the drying,
yet at the same time, owing to the deficiency in glutin, the
binding power will be low. The higher the percentage of
glutin in a glue, the higher is the melting-point of the jelly, and
as this is an indication of its strength, it follows that a bone
glue in which chondrin is predominant is inferior to a hide glue
as a cement. A good glue should be well dried and free
from smell ; and when immersed in cold water for twenty-four
hours it should absorb from nine to eleven times its weight
of the water, and when dissolved in hot water to the extent
of J.I per cent, the jelly formed on cooling should be firm
and consistent, and capable of sustaining a weight varying
from 1^ to 2 Ibs. Glue should not become damp in ordinary
air, or it is liable to turn mouldy, and this fault would
indicate impurity or adulteration. Further, in the manner
of breaking, a splintery fracture shows that the glue is not
well boiled, while judging from the appearance is apt to
produce a wrong estimate of its value, for a glue without gloss
and very much warped may be excellent in adhesiveness and
tenacity. From every batch of glue made a sample cake
should be drawn, labelled with a number and date, and kept
for future reference, the particulars, along with a record of
the testing, being entered in the laboratory journal. A full
114 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
examination, whether of a hide or bone glue, comprises
Moisture, ash, water-absorbing power, strength of jelly (shot
jelly test), melting point of jelly, capacity for drying, foreign
matter, acidity, viscosity, fatty matter, glutin, breaking strain,
and foam test. The colour, shrinkage, and smell should also
(a) Moisture. Ordinary glue of good quality contains
14 to 1 8 per cent, of water ; a lower amount indicates over-
drying, which injures the tenacity, while a high percentage
diminishes the keeping qualities. For determination, a portion
of the cake is taken and crushed to a coarse powder in a
Wedgwood mortar, and then to a fine meal in an agate mortar.
Of the meal 5 grams are weighed in a tared watch-glass,
and exposed to a temperature of 110 C. in the air oven
for twelve hours. On cooling and weighing, the difference
in weight represents the moisture in the 5 grams taken,
and from the result obtained the percentage is readily
(6) Ash. In a tared platinum crucible, 5 grams of the
powdered glue are weighed, and slowly heated until com-
pletely carbonised ; the crucible is then transferred to a
muffle furnace and heated to a bright redness for ten hours,
cooled, and weighed. The increase in weight of the crucible
is the amount of ash yielded by the weight of sample taken,
and ranges from 2 to 3 per cent. Sometimes sulphate and
carbonate of lead, zinc oxide, and the salts of chromium and
tungsten are added to the glue before jellying, with the
object of increasing its adhesive properties. These ingredients
are found in and thus increase the weight of ash. A quali-
tative examination of the ash will give a clue to the origin
of the glue. The ash from bone glue fuses by the heat of the
Bunsen flame, and is mainly composed of the phosphates of
calcium and magnesium. On the other hand, the ash from
a hide glue does not fuse when heated, owing to the presence
ANALYSES OF THE RAW AND FINISHED PRODUCTS. 115
of caustic limes derived from the 'liming' of the skins.
The ash is also alkaline and free from phosphates.
(e) Water -absorbing power. A portion of the sample cake,
in one piece, is weighed, and then immersed in cold water
having a temperature of 4 C. for twenty-four hours (a very
thick cake will require from thirty-six to forty hours). Then
carefully remove, drain off all superfluous water, and weigh.
The increase in weight is the amount of water taken up
mechanically by the glue, and the greater this absorption,
the more economical will the agglutinant be found when in
use. Fine glue made from white bones will take up from
eight to nine times its weight of water, while common German
bone glue will only absorb four to five times. In a good
hide glue the absorption will reach to eleven times its weight.
(d) Strength of jelly (shot jelly test), Lipowitz's method.
This test depends on the weight-sustaining power of glue
made into a jelly of known strength. The sample made
into a solution of 10 per cent, strength is run into a glass
cylinder of uniform width to gelatinise. The cylinder, which
should be surrounded by a water jacket to maintain a
definite temperature, is covered with a cap at one end. The
cap is perforated, and through the perforation is passed
freely a stout iron wire, at the lower end of which is soldered
a piece of tin dipped like a saucer, the convex side resting
on the surface of the jelly formed by the cooling of the glue
solution. To the upper end is also soldered a similarly
shaped piece of tin to hold the weights necessary to force
down the wire. The whole apparatus weighs about 10 grains,
and is loaded gradually with weights or small shot until the
convex side of the saucer-shaped piece of tin is forced into
the jelly. The greater the strength of the jelly, the greater
will be the weight required. A high-grade glue when made
into a jelly will carry as much as 60 grams, while the jelly
of a poor quality of glue will sustain only 8 grams.
116 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
A commercial form of the above test, known as the c shot
jelly test/ is made by cooling a 10 per cent, solution in an
ice-box for three or four hours till firmly set. A tube or
small pan is placed on the jelly and loaded with shot till it
sinks. The weight of shot used is a measure of the strength
of the glue.
(e) Melting-point of jelly. Kissling's method, which gives
the most satisfactory results, is made under standard con-
ditions. The test is carried out by weighing 15 grams of
the sample, and allowing it to stand in 30 c.c. of water for
twelve hours in a flask. The solution is then completed
by immersing the flask in boiling water and shaking well.
While still liquid some of the glue solution is poured into a
test tube, which is then closed with a cork. A similar tube
is filled to an equal extent with a concentrated (1-1)
solution of best hide glue, and a thermometer is inserted in
it. These tubes are immersed for an hour in water at 15 C.,
and are then placed in a bath of special construction. This
consists of a round metal water-bath, which is filled to a
mark with water maintained at a temperature of 50 C. On
to the top of the bath a shallower vessel of equal diameter
fits as a lid. The bottom of this is covered with asbestos,
and in it are placed horizontally the tubes containing the
glues and the thermometer. A plate of glass covers the
whole. The melting-point is taken as the point at which
the surface of the glue leaves its vertical position and becomes
distinctly inclined. The melting-point varies with the
amount of glutin present.
(/) Capacity for drying. Twenty grams of the sample are
dissolved in a little hot water, and then made up to
100 c.c., and the temperature noted. Ten c.c. of the solution
are taken, spread on a large watch-glass, and allowed to stand
in a room free from dust and not exposed to frequent change
of temperature. A standard solution of the same strength
ANALYSES OF THE RAW AND FINISHED PRODUCTS. 117
and temperature is made from a high grade of glue, and 10 c.c.
of the solution are taken and placed on a watch-glass. The
behaviour of the sample jelly is compared with that of the
standard during the several days' exposure of the two
(g} Foreign matter. The foreign matter of glue is of an
insoluble mineral and organic nature, and is determined by
dissolving 5 grams of the sample in hot water and transferring
to a glass cylinder holding 1000 c.c., and made up to the
litre mark with hot water. The cylinder is immersed in hot
water to prevent the solution from congealing. On standing
for ten hours, the whole of the insoluble impurities fall to
the bottom. The clear liquor is run off and the sediment
decanted on to a tared filter, well washed with hot water to
remove all trace of glue, and then dried at 105 C. in the
air oven. On cooling and weighing, the increase in weight
of the tared filter represents the foreign or insoluble matter
in the sample taken. The foreign insoluble matter is
greater in bone than in hide glues, the latter rarely exceeding
2 per cent.
(h) Acidity. Fifty grams of the sample are suspended in
a flask in 80 c.c. of cold water for ten hours. The flask is
connected with a condenser, and the volatile acids are driven
over by a current of steam, the condensed acids and water
running into a graduated cylinder. When the distillate
amounts to 300 c.c. the distillation is discontinued and the
contents of the cylinder titrated with deci-normal alkali.
In presence of sulphurous acid, the cylinder should contain
a known quantity of the standard alkali, added previous to
the distillation. The acidity is due to hydrochloric and
sulphurous acids, and the sample should not contain more
than '20 per cent, of these acids.
(i) Viscosity. The viscosity of a glue solution of known
strength is the length of time taken by the solution to flow
118 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
through a burette as compared with water taken at twenty-
five seconds in running through the same. The sample of
glue is dissolved in hot water to a strength of 1 per cent.,
and the solution cooled to 18 C., and 50 c.c. run through a
burette, the number of seconds required being the viscosity
of the solution. The higher the strength of the sample, the
greater will be the length of time required for the 50 c.c.
of the glue liquor to pass through the orifice of the burette.
With a strong glue thirty-two to thirty-four seconds are
needed, a medium quality twenty-eight to thirty seconds,
while the solution of a weak glue flows through in twenty-
six to twenty-seven seconds.
(/) Fatty matter. For many industrial applications the
small proportion of fat sometimes met with in bone glues is
objectionable. The determination is made in the Soxhlet
apparatus, as described on page 109, on 5 grams of the
(k) G-lutin. According to Rideau, the organic matters of
glue are very complex. Among the nitrogenous matters to
be found in it there are probably several varieties of glutin
and chondrin, as analyses of these substances, presumably
pure, show differences in elementary composition, in addition
to the variation in physical properties. Products of change,
such as albumoses and peptones, are usually present, with
small quantities of bases, sugars, and ill-defined bodies. For
this reason the content of nitrogen and the various processes
of precipitation by tannin and other agents, yield results
which have but only an approximate relation to the com-
mercial value, for not only is the glutin estimated, but also
the peptones and other non-gelatinous nitrogenous matters
are thrown down or co-estimated, while the tannates of glutin
are too uncertain to make the method thoroughly reliable.
These methods may be enumerated as follows (Trotman and
ANALYSES OF THE RAW AND FINISHED PRODUCTS. 119
(1) Determination of total nitrogen by Kjeldahl's process
and calculation to glutin.
(2) Determination of total nitrogen by soda-lime.
(3) Precipitation by tannin, and either measuring the
nitrogen in the precipitate, or titrating excess of tannin in
(4) Precipitation by chlorine and determination of nitrogen
in the precipitate.
In the estimation by tannin 10 grams of the sample are
weighed (preferably in one piece), and then immersed in
cold water for ten hours, the water being changed two or
three times to remove any colouring matter in the glue.
On dissolving in hot water and pouring into a beaker, the
solution is precipitated with tannic acid, forming a dense
white precipitate, which, on washing with hot water by
decantation three or four times, is then poured on to a tared
filter, washed again with a little hot water, and finally dried
at 105 C. for ten hours in the air oven. The precipitate of
tannate of glutin, when dried, has a composition of
Glutin, . . . .4274 per cent.
Tannin, .... 57'26
and from those data is calculated the weight of glutin in the
The Bisler-Beaumat method of tannin titration is as
follows : Two solutions are prepared : (a) 10 grams of pure
tannin are dissolved and the solution made up to a litre; (b) 10
grams pure isinglass and 20 grams of alum are dissolved and
diluted to a litre. The latter solution is added to a measured
quantity of the former till no further precipitate is produced ;
the volume used is then read off on the burette. The same
volume of tannin is then precipitated by a 1 per cent,
solution of the glue ; the relation between the volumes of
the glue solution, and the isinglass, gives the ratio of the
glue to the sample of isinglass taken as a standard.
120 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
(1) Breaking strain. In determining the breaking strain
of a glue joint, Bruxchanger devised a sliding or lateral test
in which two pieces of red beech a decimetre square were
glued together with their fibres parallel and their surfaces
overlapping one centimetre. The pieces were fixed in a
weeder's testing machine and forced in a direction parallel to
their surfaces till the glue yielded and the pieces slid over
Rideau adopts the following method. For the testing
blocks a hard, and yet moderately porous, biscuit stoneware
is used in place of wood. They are in the shape of a
truncated wedge fitting the claws of a glue tester having
a system of levers and a weight tub to hold the shot. In
making the test, 1 part of glue broken in small pieces is
soaked in 2 parts cold water for six hours, then raised to
70 C., agitated until dissolved, and afterward quickly strained
through fine muslin. The plane surfaces are then soaked in
this solution for half an hour, joined carefully with light
pressure, and the pairs mounted in a frame between uprights,
each pair being cautiously loaded with a weight of 5 Ibs., and
the whole kept for five days in a cool and dry room. At the
end of that time they are mounted in the testing machine,
the utmost care being taken to avoid jerking, A to put on the
weight gradually, and to keep the lever horizontal. An
improvement on the shot would be a hopper with dry sand
or mercury flowing through a regulated orifice, with an
automatic cut-off at the moment of fracture, which is
generally sudden. By this method a high-grade brown
Scotch glue gave, with four different pairs of stone blocks,
a breaking strain of 675 Ibs., 663 Ibs., 712 Ibs., and 645 Ibs.
per square inch.
A rough method of determining the breaking strain of a
glue, without apparatus, is to cut transversely with a fine
saw a stick of wood 1 inch square, to glue the cut surfaces
ANALYSES OF THE RAW AND FINISHED PRODUCTS. 121
together, and mount them on end with a moderate weight on
top. After three days the bar is laid across the supports and
weighted gradually in the middle till fracture ensues.
(ra) Foam test. In certain classes of work the frothing or
foaming of a glue solution is a great disadvantage. It is
determined by vigorously stirring for three or four seconds
with a glass rod a 10 per cent, solution of the glue, the
height of the foam formed measured in inches, and the rate of
its disappearance noted. Some glues when in solution show
half an inch of foam, others one-eighth, and some none
Gelatine. When used in confectionery or manufacturing
work, gelatine is examined for moisture, ash, water-absorbing
ppwer, fatty matter, and acidity, by the processes described
For testing the purity of a gelatine, Vogel adds ammonia
to a 10 per cent, solution of silver nitrate till the precipitate
is re-dissolved, and mixes this liquid with an equal volume
of the solution of gelatine under examination. If the
gelatine is impure, the mixture takes a yellow or even a
Degelatinised Bones. According to the object in view,
the degelatinisation for glue may be wholly or only partially
carried out. With a carbonising plant at his disposal, the
manufacturer extracts only a portion of the nitrogenous
carbon as glue, the remainder being left in the bones for
(a) Wholly degelatinised. When the bones are used
solely for glue, the examination is confined to nitrogen and
phosphate of lime. In preparing the sample for analysis,
seven to eight handf uls, representing an average of the whole,
are taken and intimately mixed on a sheet of paper, and from
this mixture a portion is reduced to a powder by grinding in
122 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
(aa) Nitrogen. The estimation is made by Kjeldahl's
method (see ' Raw Bones/ c.) on 5 grams of the powdered
(bb) Phosphate of lime. Weigh into a porcelain basin or
small beaker 5 grams of the sample, mix with 10 c.c.
concentrated hydrochloric acid, and evaporate to dryness
on the water-bath to render the silica insoluble.
To the residue add 4 c.c. strong hydrochloric acid, then
20 c.c. water, warm, and then filter off the insoluble silica ;
wash well with hot water, and in the filtrate precipitate
the phosphoric acid by (1) ammonio-citrate of magnesia, or
(2) molybdate of ammonium. The solution of ammonio-
citrate of magnesia is prepared by dissolving 270 grams of
citric acid in hot water, and adding slowly 27 grams of
carbonate of magnesia. The heating is continued until the
effervescence has ceased and the carbonic acid has been
wholly driven off, then filtered into a lifp' flask, cooled to
15*5 C., and 400 c.c. of a 10 per cent, solution of ammonia
added, the whole being made up to the litre mark with
cold water. To the hydrochloric acid filtrate, ammonia is
added until strongly alkaline, and then 100 c.c. of the citro-
magnesic solution, the contents of the beaker being vigorously
stirred until the white precipitate of phosphate of magnesia
appears. Allow to stand for six hours, then filter off the
precipitate, and wash well with cold water containing 2 per
cent, of ammonia. Dry, ignite, and weigh as pyrophosphate
of magnesia. On multiplying the weight obtained by
T3964, the factor for conversion, the result is the weight of
tri-calcic phosphate in the sample taken, and from this the
percentage is readily calculated.
In using the molybdic method, which is quite as accurate
as the citro-magnesic process, the solution of molybdate of
ammonium used is prepared by dissolving 1 gram of molybdic
acid in 4 grams of ammonia (sp. gr. 0*96), the solution being
ANALYSES OF THE RAW AND FINISHED PRODUCTS. 123
slowly poured into 15 grams of nitric acid (sp. gr. 1'20),
which must be shaken constantly to prevent separation of
molybdic acid. After two days' standing, the clear solution
is syphoned off for use. To the hydrochloric acid solution
of the phosphates add 10 c.c. nitric acid, and evaporate to
dryness. Now add about 6 c.c. nitric acid, and treat the
liquid with 150 c.c. of the solution of molybdate of ammonium,
and stir well. If the yellow precipitate of phosphate of
molybdenum is slow in coming down, add a little ammonia ;
if too much is used, dissolve any precipitated ferric hydrate
formed with a few drops of nitric acid. Allow to stand for
eight hours, and then filter. Wash the whole of the pre-
cipitate with a mixture prepared by dissolving 15 grams of
nitrate of ammonium in 100 c.c. of water, and adding to the
solution 5 c.c. strong nitric acid and 10 c.c. of the molybdic
solution. When completely washed, the precipitate is
dissolved on the filter in dilute warm ammonia. The
filtrate is then nearly neutralised with hydrochloric acid,
and the phosphoric acid in solution is precipitated with
magnesia mixture. After filtering, the precipitate of
phosphate of magnesia is washed with a 2 per cent, solution
of ammonia, and is finally dried, ignited, and weighed as
pyrophosphate of magnesia, the tri-calcic phosphate being
calculated as in the citro-magnesic method.
The magnesia mixture is prepared as follows : Dissolve
83 grams of crystallised sulphate of magnesia in boiling
water, add 5 c.c. of hydrochloric acid, and then 82 grams of
crystallised chloride of barium previously dissolved in water.
Filter off a few drops of this solution and add dilute
sulphuric acid ; if this gives a precipitate, add a little more
sulphate of magnesia. Then decant and filter, mix the filtrate
and washings, and concentrate by evaporation on the water-
bath. When cool, transfer to a litre flask, add 165 grams
of pure chloride of ammonium, 260 c.c. of ammonia, and then
124 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
water to the mark. Allow to stand for a few days, and filter
(&) Partially deyelatinised. The object of the manufacturer
being charcoal, this product is tested for moisture, carbon,
silica, and iron. Animal charcoal possesses the property of
absorbing organic colouring matter from solutions brought
in contact with it, and this decolorising power depends on
the nitrogenous carbon it contains. A good charcoal should
contain no more than 11 per cent, of carbon, and no less than
10 per cent. The iron should not exceed *2 per cent., and
the silica '5 per cent. It is sold on a basis of 8 per cent,
(aa) Moisture : The moisture is determined as iinder ' Raw
Bones (a)/ on 3 grams of the powdered sample.
(lib) Carbon and silica : Two grams are weighed in a small
beaker, and heated for an hour with hydrochloric acid, then
filtered through a tared filter paper, the residue left on the
filter being well washed with hot water until the filtrate
is free from acid. Dry at 105 C. for ten hours, cool, and
re-weigh. The increase in weight is the undissolved carbon
and silica. To separate the two substances, the filter paper
containing the residue is folded up and placed in a tared
platinum crucible, slowly carbonised over the Bunsen flame
for an hour, and then heated to bright redness in a muffle
for ten hours. The carbon is completely burned to carbon
dioxide, leaving a residue of silica, along with the ash of
the filter paper, in the crucible. Cool and re- weigh. The
increase is due to the silica and ash, and on deducting the
latter, the former is readily calculated. From the weight of
the filter paper plus the residue of undissolved carbon and
silica the tare of the former is subtracted, and from the net
weight obtained the combined percentage of carbon and
silica is made. On deducting from this calculation the
percentage weight of silica found, the difference is the
ANALYSES OF THE RAW AND FINISHED PRODUCTS. 125
percentage amount of carbon in the sample under exa-
(cc) Iron : In the acid filtrate from (bb) the iron, which
exists as ferric chloride, is precipitated in the usual way as
hydrate, the precipitate washed with hot water, dried,
ignited, and weighed as ferric oxide. From the weight
obtained the percentage amount of iron in the sample is
Manures. For manurial purposes wholly degelatinised
bones are generally converted into superphosphates by
treatment with sulphuric acid, which renders a portion of
the phosphoric acid soluble. In preparing the different
special manures used in agricultural work the superphosphates
are mixed with varying proportions of nitrogen (either as
organic nitrogen, nitrate of soda, or sulphate of ammonium)
and potash salts.
The examination of bone superphosphates is confined to
soluble and insoluble phosphates, while in the special or mixed
manures the estimation is made of the soluble and insoluble
phosphates, nitrogen, and potash.
(a) Soluble phosphates. A portion of the average sample
taken is ground to a fine state of division in an agate mortar,
and 5 grains are weighed out into a porcelain mortar,
triturated with a small quantity of cold water, the liquor
then passed through a filter paper into a litre flask. The
rubbing with water is repeated four times to exhaust the
soluble phosphates, and then the contents of the mortar are
washed on to the filter paper, and the washing continued
until a drop of the filtrate shows no precipitate with
molybdic solution The litre flask, which will now be about
half full, is made up to the mark with cold water at 15'5 C.,
and 100 c.c., representing '5 gram of the sample, are with-
drawn by a pipette for the analysis, which is made by the
citro-magnesic or the molybdic method as described under
126 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
' Degelatinised Bones ' (bib). By either method the soluble
phosphates are estimated as tri-calcic phosphate.
(&) Insoluble phosphates. The residue on the filter paper
left from (a) is washed into a small beaker with hydrochloric
acid, the contents evaporated to dryness on the water- bath,
a few drops of hydrochloric acid added and 5 c.c. of water,
and the whole filtered to remove the insoluble silica. In
the filtrate the insoluble phosphates are estimated by the
citro-magnesic or molybdic process as above described.
Calculate the result as tri-calcic phosphate.
Nitrogen. If the nitrogen is derived from added nitrogen-
ous matter, it is estimated in 3 grams of the powdered
sample by Kjeldahl's method as given under ' Eaw Bones ' (c).
If in the form of sulphate of ammonium, the ammonia is
distilled with milk of magnesia in a flask connected to a
Liebig's condenser. The distillate is absorbed in 20 c.c. of
standard sulphuric acid, and the excess of acid determined
by titration with standard soda solution. The ammonia
found is calculated to nitrogen. When existing as nitrate of
soda, 2 grams of the powdered sample are mixed with 12
grams ignited sand (white). The mixture is placed in a tared
platinum crucible and ignited strongly by a foot-blowpipe
for twenty minutes. On cooling and re-weighing the crucible,
the loss (minus the moisture previously determined on the
weight of sample) represents nitric acid, from which the
percentage of nitrogen is calculated.
The estimation can also be made by Schloesing's method,
which is based on the action of ferrous chloride and hydro-
chloric acid on any solution containing nitrate of soda, the
nitric oxide formed being collected and measured in a
graduated glass cylinder. From the nitric oxide found, the
corresponding amount of nitrogen is calculated.
Potash. In estimating the potash present in manures,
the method adopted by Griffiths yields very accurate results.
ANALYSES OF THE RAW AND FINISHED PRODUCTS. 127
Ten grains of the powdered manure are taken and boiled in
300 c.c. of water for ten minutes. Allow to cool, dilute
with water to a litre, and filter. Take 100 c.c. of the filtrate
(equal to 1 gram of the sample), add 50 c.c. water, and heat to
100 C. Now add, drop by drop with constant stirring, a
slight excess of barium chloride, without filtering, and then a
solution of barium hydrate, also in slight excess. Heat, filter,
and wash the precipitate. Add to the filtrate 1 c.c. of strong
ammonia, and then a strong solution of ammonium carbonate,
and heat. At this point add *75 gram of ammonium oxalate,
in fine powder. Filter, wash ; then evaporate the filtrate to
dryness in a platinum basin, and ignite at a low temperature.
Digest the residue with hot water. Filter, and wash with the
smallest quantity of water possible. Add to this filtrate in
a 'porcelain basin a drop or two of strong hydrochloric acid,
and then from 5 to 10 c.c. of platinic chloride solution. Now
evaporate on the water-bath to a thick syrup, add a little
alcohol of 95 per cent, strength, wash by decantation, collect
on a filter, wash with strong alcohol and then with 5 c.c. of
ether, dry for half an hour at 100 C., and weigh as potassio-
platinic chloride. If any white foreign matter forms in the
potassio-platinic precipitate, it must be washed with 10 c.c.
of a half-saturated solution of ammonium chloride which has
been saturated with potassio-platinic chloride, and finally
with alcohol and ether. The precipitate is then dried and
In estimating the potash, multiply the weight of potassio-
platinic chloride found by 0*19308, for chloride of potassium
Fuel. The consumption of fuel in the generation of
steam, not only for motive purposes, but also for the many
operations in which boiling or steaming is a necessity, forms
an item of primary importance in the cost of conducting a
works. As a matter of economy it then becomes necessary to
128 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
examine the heating power of the fuel used from time to
time, so that any waste may be avoided.
The heating power of a fuel is found (a) by the use of a
calorimeter (preferably Thompson's), in which a sample of the
coal is burnt and its heating power determined directly from
the experiment; (b) by estimating the moisture, ash, fixed
carbon, and volatile combustible matter.
From these results the corresponding thermal value is
calculated, and this, when divided by 966 (the latent heat of
steam at 100 C.) gives the equivalent water evaporated
from and at 100 C. per pound of combustible used.
When the moisture and ash are low in a fuel, the
following simple process for estimating the heating power
yields fairly good results. In detail (says Stedman) the
process is as follows : 1 gram of the finely powdered coal is
intimately mixed with 30 grams of litharge, transferred to a
No. 3 Hessian crucible, 20 grams more of the litharge placed
on the top of the charge, the crucible covered up and heated
to redness in a furnace for fifteen minutes. The crucible is
then removed, allowed to cool, broken, and the button of
metallic lead cleaned from the slag and carefully weighed.
Duplicate results should not vary more than 0'025 gram.
To calculate the result, 1 gram of carbon reduces thirty-four
times its weight of lead, and if 1 kilogram of carbon equals
8140 calories, then each gram of lead is equivalent to
= 239 calories. Suppose the lead button from the gram of
coal weighed 31 -05 grams, then ^^ x 31'05 = 7420*9 calories
per kilogram, or 133577 British thermal units (B.T.U.) per
pound of fuel, which represents the heating power of the coal.
In practice, the heating value that can be obtained depends
on the efficiency of the boiler, and this largely upon the
difficulty of thoroughly burning the volatile combustible
ANALYSES OF THE RAW AND FINISHED PRODUCTS.
matter in the boiler furnace. Supposing the boiler efficiency
was 65 per cent., then the evaporation per pound of coal
from and at 100 C. would be 1442 x 0'65 = 9'37 Ibs.
Note. A calorie is the standard heat unit, and represents
the heat required to raise the temperature of one kilo-
gramme of water from 4 C. to 5 C.
A British thermal unit (B.T.U.) is the heat required to
raise the temperature of one pound of water 1 F. at its
temperature of maximum density (391 F.).
To reduce calories per kilogramme to B.T.U. per pound,
multiply by .
Valuation of Raw and Finished Products.
Raw Bones. Common bones realise from 3 to 3, 5s.
per ton. For treatment in the work they are not bought
under any guarantee as regards the phosphate of lime or
fatty and gelatinous matters they contain. These ingredients
vary according to the condition, etc., of the bones ; for
instance, fresh bones, as ribs, shoulder-blades, heads, etc.,
will yield 12 J per cent, of fat and 16 to 18 per cent, of
glue ; but with semi-boiled or kitchen bones which have
undergone a partial degreasing and degelatinising, the yield
is only from 6 to 8 per cent, of the former and 10 to 12
per cent, of the latter.
For manurial purposes, especially on light soils for turnips
and pasture-land, common bones have a use as half-inch
bones, quarter-inch bones, and bone-meal. They are sold
to the farmer under a guarantee of the phosphate of lime
and nitrogen they contain, these ingredients varying from
48 to 50 per cent, and 3J to 4 per cent, respectively.
Marrow bones, or 'knuckles,' realise from 6 to 6, 5s.
per ton, owing to their richness in fat and their value, after
a partial degreasing and degelatinising, in the manufacture
130 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
of buttons, knife-handles, paper knives, and many other
Bone fat is sold at the ruling market price, on a basis of
98 per cent, pure fat ; the 2 per cent, of impurities allowed
consists of water, ash, and organic matter of a non-fatty
nature. Colour being of no importance, dark-coloured
benzene-extracted fat is used largely in the manufacture
of stearine for candles and glycerine, while the lighter-
coloured steam-extracted fat is made into soap, etc,
Tanners' Wastes. Tanners' wastes, such as the parings
of hides, the ears and refuse trimmings of thick hides, yield
on an average from 45 to 50 per cent, of glue. They are
not bought on any guarantee, but an estimation of their
glue-yielding capacity is sometimes made in a small experi-
mental plant consisting of a set of vats with which are
connected a filter press, vacuum pan, and drying stove. A
determination made in this manner is a safe guide to what
the raw materials will yield when worked on the large scale.
Gantter, in making a chemical test of the value of tanners'
wastes for glue-making, boils 100 grams of the sample with
a litre of water and a few drops of soda till completely
exhausted, makes up to 2 litres, and allows to stand for ten
hours at a temperature above the jellying point of the
solution. The insoluble matter settles to the bottom, while
any fatty matter forms a film on the surface. The residue
and ash are determined in 20 c.c. of the solution, while another
20 c.c. sample diluted with hot water, made neutral with
acetic acid and precipitated with tannin, filtered, and any
excess of tannin in the filtrate withdrawn by hide powder,
dried, and the ash determined, gives the organic non-glue-
Manures. -In the wholesale manure industry, phosphates,
whether of bone or mineral origin, nitrogen, as sulphate of
ammonia, nitrate of soda, or insoluble nitrogenous matter;
ANALYSES OF THE RAW AND FINISHED PRODUCTS. 131
potash, as sulphate, muriate, or as kainite, are purchased at
a market price per ' unit,' and this value varies according
to the source of the material and its solubility.
If a superphosphate is sold containing 30 per cent, of
tri-calcium phosphate rendered soluble by sulphuric acid, it
means in the scale of unit values 30 units at the agreed
price, and supposing the selling price per unit was Is. 6d.,
the value of the superphosphate would be 2, 5s. per ton.
Knowing the unit value of soluble phosphate, nitrogen,
and potash, derived from various sources, the way to
calculate the money value of a manure is to make its
constituents, as given in the analysis, represent 100 tons.
The amount of each ingredient is multiplied by its price
per ton, and all the products added together give the value
of 100 tons. This result divided by 100 gives the value
of one ton.
Under clause 1, section 1, ch. 56 & 57 Viet., all manures
are guaranteed by analyses, but the seller only guarantees
the minimum percentage in each case. In the event of a
purchaser desiring an independent analysis of a manure,
manufacturers make it a condition of sale that the value of
an excess in any one ingredient shall be placed against the
value of a deficiency of any other, to the extent of 2 units
of either soluble or insoluble phosphate, | unit of potash, or
\ unit of nitrogen.
Manures for analyses are sampled in the presence of
buyer and seller or their representatives, within ten days of
delivery, the buyer giving three days' notice of his intention to
draw samples. In order to arrive at a fair average sample
of the bulk, a number of bags (not less than one in every five)
are emptied on a clean, dry floor, and the contents well
mixed. A quantity of not less than 20 Ibs. is then drawn
from all parts of the heap, and from this, three glass bottles
holding J Ib. each are filled, sealed, and a label affixed,
132 GLUE, GELATINE, AND THEIR ALLIED PEODUCTS.
giving such particulars as will serve to identify it with the
invoice, a copy of which is sent along with the sample for
analysis to the chemist. Another of the three samples is
given to the seller, and the third is retained for reference
in case of dispute. Manufacturers generally accept the
analyses of the chemists of the Eoyal Agricultural Society
of England, the Highland and Agricultural Society of
Scotland, or the Eoyal Agricultural Society of Ireland.
Selected Specifications of Patents relating to the
manufacture of Glue and Gelatine.
English patent No. 18,042, 1902. Improvements in the
manufacture of glue and gelatine, by Hermann Hilbert,
Henfield, Upper Bavaria.
The bones, whether or not they have been degreased and
treated for the removal of foreign substances, are mixed with
a sufficient quantity of water to form a semi-fluid mass,
which is then transferred to a vessel in which the mass may
be stirred. There is then added to it hydrochloric acid, or
a chloride, and gaseous sulphurous acid while stirring. The
chloride may be sodium chloride (common salt) or any other
alkaline chloride, and the temperature may be high or low
as may be more convenient and suitable. The mass is then
macerated and the contained insoluble phosphate of calcium
is brought into solution, while at the same time the material
is highly bleached. Because of the excess of the sulphurous
acid, the phosphate of calcium in the bones becomes de-
composed into free phosphoric acid, or double phosphate of
calcium and sulphite of calcium, while the chloride is
decomposed into hydrochloric acid and sulphite of the
alkali. The bone material is consequently affected by two
134 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
different acids hydrochloric and sulphurous acids simul-
taneously. The hydrochloric, acting to produce soluble salts,
permeates the mass and prepares it for the action of the
sulphurous acid, whereby the whole operation is shortened.
At the same time the hydrochloric acid acts upon the
produced sulphite of calcium and converts it into chloride,
sulphurous acid gas is liberated in the nascent state and acts
as a powerful bleaching agent, far more effective than simply
introducing sulphurous acid either in a liquid or gaseous
form. This is the new and important feature claimed by
the invention. The glue and gelatine are extracted in the
usual way by boiling.
English patent No. 27,053, 1902. Improvements in the
manufacture of glue and gelatine, by Kichard Arens,
Ph.D., Euhrort, Germany.
The methods hitherto employed for extracting phosphate
of calcium from bones and the like in the manufacture of
glue and gelatine consist in treating the material with dilute
hydrochloric acid. The phosphate of calcium is dissolved
out, forming monobasic phosphate of calcium and chloride
of calcium, and there remains behind the pure cartilage or
gristle, which is suitable for further manufacture as a
substance capable of yielding glue. The method has the
disadvantage that the hydrochloric acid employed is lost in
a solution of chloride, and hitherto it has not been possible
to employ any suitable means for the recovery. Consequently,
for a long time past watery sulphurous acid has been
employed in order to free the bone material from the lime
salts. The technical difficulties in dissolving with sulphurous
acid are, however, considerable. The decomposition proceeds
so slowly that even where a very considerable excess of
acid is employed, in case it is desired to entirely free the
bone from lime, it takes eighty to ninety days to carry out
the operation. The inventor has, however, found that the
reasons for the weak action of the acid on the bones is that
the sulphurous acid solution, which at its maximum strength
contains only 43 J vols. of sulphurous acid gas, in acting on
the material, first forms neutral calcium sulphite. This
substance is insoluble in water, and is held in solution only
by an excess of sulphurous acid, but its solubility ceases
as soon as free sulphurous acid present attacks further
quantities of the lime, and the monobasic phosphate of calcium
commences to saturate the lye. The calcium sulphite is then
precipitated, and encrusts the bone material. If then fresh
solutions of sulphurous acid be added, the precipitated
calcium sulphite must be dissolved in the sulphurous acid.
When this has been done, the acid solution can again form
fresh quantities of calcium sulphite, and bring into solution
acid phosphate of calcium. The point is again reached
where the calcium sulphite can no longer be held in solution.
It is thus evident that the lye, which contains an excess of
free sulphurous acid in large quantities, cannot be strength-
ened further and no longer acts on the bone material, but
diminishes in its strength. By this precipitation of the
calcium sulphite and re-dissolving of the same, as already
stated, a long time is required for completing the operation,
together with an excess of acid, which exceeds the theoretical
quantity by 50 per cent. The present process allows of the
material being dissolved in a very much shorter time, with
a very small apparatus and the theoretical quantity of acid,
but the bone material must be treated with sulphurous acid
dissolved in water, the liquid being simultaneously subjected
to pressure. By this means the sulphurous acid solution is
much stronger in the percentage of gas, and the encrustation
of the bone material is also avoided, because the lye formed,
which is subjected to pressure, has no tendency to crystallise
out, owing to the excess of sulphurous acid held in solution.
136 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
and because the pressure is capable of holding the calcium
sulphite in solution to a greater degree. This process differs
from processes already known, in that the phosphate of
calcium more particularly is easily and rapidly dissolved
out by a cold process, so as to leave behind the glue-forming
substance to be extracted in the usual way.
English patent No. 18,742, 1903. Improved process of rendering
or reducing fish waste and other material capable of
yielding grease, oil, or glue.
The primary object of the invention is to extract liquid
products from material of the character indicated, rapidly
and thoroughly, by heating the material in a closed receptacle
and subjecting it during treatment to a pneumatic pressure
greater than the pressure which results from the heating of
the material, and when the mass has caked or become closely
packed to such an extent as to materially retard the flow of
oil or extracted product, introducing into the mass air or
aeriform liquid under a pressure greater than the first
English patent No. 22,069, 1903. Improvements relating to
vegetable gelatine and the process of manufacturing the
same, by Albert Martin, Clinton, Iowa, U.S.A.
This invention relates to a certain new and useful
improvement in the manufacture of gelatine from moss.
The moss selected is a waste product known as Irish moss,
which contains mucilaginous and albuminous matter, as well
as cellulose, mineral matter, and water, and is subjected to a
treatment which produces a gelatine, or food product, which
when used with milk will not coagulate the latter, and hence
requires no soda. The moss is thoroughly washed, cleansed
from all sand and other impurities, bleached (preferably in
the sun), boiled in water, strained, and the resulting liquid
boiled down to a syrupy consistency. The syrup is after-
wards spread out upon large pans, and subjected to a gentle
heat, whereby large sheets resembling isinglass are produced.
This is then shredded. When treated like other gelatine it
dissolves readily and gives a superior jelly.
138 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS,
TESTING OF GLUE AND GELATINE (Trotman and Hackford).
by ZnS0 4 .
Gelatine No. 1,
Glue No. 1, .
!! !', 3', '.
The second column gives the physical test, 100 being the
standard ; the third indicates the total nitrogen ; the fourth
shows the portion of nitrogen precipitated by zinc sulphate
(ZnS0 4 ), which is the true measure of the glue ; the Jast
column gives the peptonic nitrogen, which is approximately
the difference between the total nitrogen and that pre-
cipitated by zinc sulphate.
VISCOSITY OF GLUE (Fels).
Description of Sample.
Time of Efflux of
500 c.c. of a 15
per cent, solution
at 30 0. , water
taking 90 seconds.
Brown transparent glue,
Sherry - coloured trans-
Light-yellow glue plates,
Muddy glue, .
The above figures show that a dark and muddy glue may
have greater strength than a transparent glue.
17 per cent.
Skin-glue No. 1, .
" 3* '.
Bone-glue (powder) No. 1,
,, , ,, 2,
j j ) j j ^*>
Bone-glue in cakes, No. 1,
Ra i her bad
140 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
HOLDING POWER OF GLUE JOINTS (Kilmarsch).
Description of Wood.
In Kilograms per Square Centimetre.
Cut across the Grain.
Parallel to the Grain.
Fir, . .
PHOSPHATIC STRENGTH OF MINERAL PHOSPHATES,
BONE ASH, AND 'SPENT' ANIMAL CHARCOAL.
Algerian ,, . .
Belgian ,, .
Bone ash No. 1, .
Lyle's grey char (charcoal),
Fame's dark char, . .
Liverpool spent char,
Greenock char siftings,
Walker's spent char, . . .
AMMONIACAL LIQUOR PRODUCED IN THE DISTILLATION
OF BONES FOR ANIMAL CHARCOAL.
Per cent, of
Gallon of Liquor.
Weight of Sulphuric
Acid at 144 T.
required per Gallon
of Liquor in Ibs.
THE ARTIFICIAL SOURCES OF GAIN OF NITROGEN IN THE
SOIL ARE BY THE USE OF ARTIFICIAL MANURES. THE
FOLLOWING TABLE GIVES APPROXIMATELY THE SUPPLIES
OF NITROGEN FROM THESE MANURES (Griffiths).
Bones, . .
Guano, . .
Shoddy, . . .
Oil cake and cotton seeds,
142 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
STANDARD SOLUTIONS USED IN THE VOLUMETRIC
WORK OF THE LABORATORY.
Standard solutions are prepared of a normal or deci-normal
strength as required. The latter are one-tenth the strength
of the former.
(a) Normal sodium carbonate. Dissolve 53 grams pure dry
salt in water and make up to 1 litre at 15*5 C.
1 c.c. = '053 gram
-030 C0 3
= -022 . COo
(b) Normal sulphuric acid. Dilute 30 c.c. acid of 1 *84
sp. gr. to 1 litre of water at 15*5 C.
1 c.c. = '049 gram H 2 S0 4
= '040 ,, S0 3
(c) Normal hydrochloric acid. Dilute 181 grams pure acid
of I'lO sp. gr. to a litre at 15*5 C.
1 c.c. = '0365 gram HOI
= 0355 Cl
(d) Normal sodium hydrate. Take 40 grams of chemically
pure or 42 grams ordinary caustic soda, dissolve, and
dilute to a litre at 15'5 C.
1 c.c. = '040 gram NaHO
(e) Deci-normal potassium permanganate. Dissolve 3*156
grams pure salt, and dilute to a litre at 15*5 C.
1 c.c. = "003156 gram K 2 Mn 2 8
= -0056 Fe
17'85c.c. = -l Fe
(/) Deci-normal potassium bichromate. Dissolve to a litre
at 15-5 C., 4-913 grams of the dried salt.
1 c.c. = '0049 gram K 2 Cr 2 7
= 0056 Fe
= 0072 FeO
= 00127 ,, I
(g) Deci-normal silver nitrate. Dissolve to a litre at 15"5 C.
17 grams of the pure salt.
1 c.c. = -0017 gram AgN0 3
= -00355 01
(h) Deci-normal sodium thiosulphate. Take 24*8 grams of
the crystallised salt, and dissolve to 1 litre at 15'5 C,
1 c.c. = '0248 gram Na 2 S 2 3 5H 2
= 0127 I
(i) Deci-normal sodium chloride. Dissolve 5 '85 grams of the
fused salt in water, and dilute at 15 0< 5 C. to a litre.
1 c.c. = -00585 gram Nad
= 0108 ,, Ag
(j) Standard solutions for phosphates.
(a) Uranium nitrate solution :
Weigh out 35 grams crystallised uranium nitrate dissolved in
900 c.c. of water and add 25 c.c. glacial acetic acid.
(b) Sodium acetate solution :
Dissolve 100 grams of the salt in water, add 100 c.c. of acetic acid,
and make up to a litre at 15 '5 C. with water.
(c) Sodium phosphate solution :
Take 231 grams of pure crystallised salt (previously dried by pressure
between filter paper) and dissolve to a litre of water at 15 '5 C.
144 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
(d) Solution of potassium ferrocyanide (freshly prepared), used as the
indicator upon a white tile.
Water is added to the uranium solution (a) so that 20 c.c. of it are
equivalent to 50 c.c. of the phosphate solution (c) or
1 c.c. of uranium solution = '005 gram P 2 5 .
The uranium solution undergoes a change on standing, and should
be re- standardised every four or five days.
The principal indicators used in volumetric work are
phenolphthalein, phenacetin, eosin, litmus, methyl orange,
cochineal, corallin, starch, potassium chromate, potassium
ferrocyanide, and ferric chloride.
TABLE OF FACTORS FOR DETERMINING THE EQUIVALENTS
OF WEIGHED BODIES.
Ammonia (NH 3 ),
Barium sulphate (BaS0 4 ), .
Carbonic acid (C0 a ), .
Ferric oxide (Fe 2 3 ), .
Nitrogen (N), .
Ammonium sulphate (NH 4 ) 2 S0 4 , .
Ammonium chloride (NH 4 C1)
Barium oxide (BaO),
Barium carbonate (BaC0 3 ),
Sulphuric anhydride (S0 3 ),
Calcium carbonate (CaC0 3 ),
Iron (Fe), ...
Lead sulphate (PbS0 4 ),
Lead oxide (PbO), .
Lead carbonate (PbC0 3 ),
(Mg 2 P 2 7 ), -
Potassic - platinic chloride
(KaPtCla), . . .
Phosphoric anhydride (P 2 5 ),
Mono-calcic phosphate (CaH 4 P 2 8 ),
Bi-calcic phosphate (Ca 2 H 2 P 2 8 ), .
Tri-calcic phosphate (Ca 3 P 2 8 ),
Magnesium sulphate (MgS0 4 ),
Magnesium chloride (MgCl 2 ),
Potash (K 2 0), ....
Potassium chloride (KC1),
APPROXIMATE HEATING VALUE OF COALS (Kent}.
Percentage of Carbon
in the Coal, dry
. and free from Ash.
(B.T.U.) per Pound of
evaporated from and at
212 F. per pound
146 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
TABLE OF THERMOMETRIC DEGREES.
RULES FOR CONVERSION.
Fahrenheit to Centigrade, 5(F '~ 82) = C.
Fahrenheit to Reaumur, 4(F '~ 32) = R.
Centigrade to Fahrenheit, ?L^_? + 32 = F.
Centigrade to Reaumur, '- = R.
Reaumur to Fahrenheit,
+ 32 = F,
TABLE OF THE METRIC SYSTEM OF WEIGHTS
The metre is the unit in the metric system of linear
measure. It is equal to 39*37 inches. It is multiplied and
divided by 10 or some power of 10 for the higher and lower
measures of length. Thus :
10 millimetres =1 centimetre
10 centimetres = 1 decimetre
10 decimetres =1 metre
10 metres =1 dekametre
10 dekametres =1 hectometre
10 hectometres = 1 kilometre.
Or the metric linear measure rnay be given thus
10 metres =1 dekametre (dm.)
100 metres =1 hectometre (hm.)
1000 metres -1 kilometre (km.)
T V or '1 metre =1 decimetre (dm.)
r^-jj or '01 metre = 1 centimetre (cm. )
TsW or '001 metre =1 millimetre (mm.)
Measures of Capacity.
The litre is the unit for measuring the volume of liquids
and gases, and is equal to 176 pints. The units in use are
given as follows :
10 millilitres =1 centilitre
10 centilitres = 1 decilitre
10 decilitres =1 litre
10 litres =1 dekalitre
10 dekalitres =1 hectolitre
10 hectolitres = 1 kilolitre
A litre is equal to the volume of 1000 cubic centimetres.
148 GLUE, GELATINE, AND THEIR ALLIED PRODUCTS.
System of Weights.
The standard unit is called the gramme or gram. From
it the larger and smaller weights are derived as follows :
10 milligrams =1 centigram
10 centigrams =1 decigram
10 decigrams =1 gram
10 grams =1 dekagram
10 dekagrams =1 hectogram
10 hectograms = 1 kilogram
A gram is the weight of one cubic centimetre of pure
water at 4 C.
Connection between the British and Metric Units.
1 centimetre = inch 1 inch =2 centimetres
1 decimetre = 4 inches 1 foot =3 decimetres
1 metre =39 37 inches 1 yard =, metre
1 kilometre = mile 1 mile =lf kilometres
1 litre =176 pints 1 pint =f litre
1 gram = 15| grains 1 ounce = 28 "4 grams
1 kilogram = 2ilbs. lib. = 453^ grams
Conversion of Multiplier.
Inches to metres '025399
Metres to inches 39 '37079
Gallons to litres 4'543
Litres to gallons '22009
Pounds (avoirdupois) to grams . . 453 '592
Grams to pounds (avoirdupois) . . '0022
Pounds (Troy) to grams . . . . 373 "24
Grams to pounds (Troy) .... '002679
ACCESS to railway, 6.
Acid, gallo-tannic, 4.
Acidity of glue, 117.
Adhesiveness of glue, 46.
Adulterated meal, 92.
Ageing of glue, 47.
Agricultural use of superphosphates,
Algerian phosphate, 100.
Ammoniacal liquors, 67, 141.
Analyses of raw and finished products,
Analysis of benzene, 111.
bone ash, 105.
condensed water, 111.
degelatinised bones, 121.
degreased bones, 111.
fresh bones, 13.
finished fat, 14.
raw bones, 108.
Animal charcoal, 51, 67, 121, 140.
grading of, 67.
milling of, 67.
tarry and ammoniacal liquors from,
manufacture of, 66.
Archbutt-Deeley purification system,
Artificial ivory, manufacture of, 85.
Ash, analysis of, 105.
estimation of, 112.
BELTS, glue for, 77.
estimation of, 111.
Bisler-Beaumat method of tannin
Bleaching, 29, 30, 43, 49.
Boiling, effect of pressure on, 25.
Boiling- house, operations of, 21.
plans of, 23.
Bone and ivory, glue for, 74.
. gelatine, 48.
superphosphates, 93 et seq.
effect of, on land, 97.
Bones, analysis of, 13.
South American, 12.
treatment of, in gelatine, 49.
Bottle tops, 76.
Brass, glue for, 78.
Brazilian isinglass, 57.
Breaking strain of glue, 120.
British and French glue, comparison
Brunn-Lowener water softener, 7.
CALVES' foot jelly, 48.
Capsules, manufacture of, 84.
Carbonisation of bones, 66.
Cast glue, 32, 43.
Celery and onion manure, 102.
Cement, jeweller's, 76.
Cements, 69, 74.
Charcoal, 51, 67, 121, 140.
grading of, 67.
Chondrin, composition of, 4.
Chrome glue, 73.
Clarification of glue liquors, 24,
Cleanser, mechanical, 19.
Cleansing of bones, 18.
Coating pills with gelatine, 84.
Cohesive strength of glue, 46.
Colour of glue, 47.
Colouring gelatine, 50.
Composition of an all round fertiliser,
animal charcoal, 68.
barley and oat manure, 102.
bone ash, 103.
bone meal, 92.
bone superphosphates, 93.
celery and onion manure, 102.
cereal manures, 101.
coarse bone meal, 19.
degreased and degelatinised bones,
dissolved bone ash, 103.
finished fat, 18.
fish residues, 90.
fresh bones, 13.
French and British gelatines, 53.
marrow fat, 65.
Peruvian guano substitute, 97.
potato manure, 100.
sugar cane mixture, 102.
Composition of turnip manure, 100.
and mangel manure, 100.
wheat manure, 101.
Concentrated size, 56.
Concentration of glue liquors, 25.
Confectionery, examination of gela-
tine for, 121.
Constitution of glue, 2.
Consumption of fuel, 1 27.
Court plaster, 60.
Cutting glue, 30.
by wire, 31.
by Schneible machine, 30.
DECOLORISATION by animal char-
Degelatinisation of bones, treatment
of, 94, 121.
Degreased bones, analysis of, 111.
carbonisation of, 66.
Degreasing of bones, 13.
modern plant for, 14.
Diamond cement, 60.
Digesting bones, 49.
Disposal of waste products, 61.
Dissolved bone ash, 105.
Dissolving glue, 45.
Drying glue jelly, 32, 43.
EFFLUENTS, treatment of, 61.
Elastic glue, 74.
Electric light in factories, 6.
Estimation of acidity of glue, 117.
ash (glue), 112.
breaking strain of glue, 120.
capacity of glue jelly, for drying,
carbon and silica in degelatinised
fatty matter in glue, 118.
foreign matter in glue, 117.
insoluble phosphates in manures,
iron in degelatinised bones, 125.
melting point of glue jelly, 115.
moisture in benzene, 111.
degelatinised bones, 124.
raw bones, 109.
refined fat, 112.
mineral matter in fat, 112.
Estimation of naphtha in fat, 112.
nitrogen in degelatinised bones,
raw bones, 110.
organic matters, not fat, in refined
potash in manures, 126.
soluble phosphates in manures,
strength of glue jelly, 115.
value of glue, 113.
viscosity of glue, 117.
water-absorbing power of glue, 115.
Ether as a solvent, 14.
Evaporating apparatus, 25.
Extracted fat, composition of, 65.
FAT, composition of, 65.
estimation of the raw bones, 109.
yield of, 13.
Fats, analyses of finished, 18.
solvents for, 14.
Fatty matter in glue, 118.
Fehling's solution, 45.
Finished fat, analyses of, 18.
Finished products, valuation of, 129.
Fish glue, 44.
viscosity of, 45.
Florida phosphate, 106.
Foam test for glue, 121.
Foreign matter in glue, 117.
Formation of glue, 2.
Fremy's analysis of bones, 12.
French and British gelatines, com-
parison of, 53.
Fresh bones, analyses of, 13.
Frozen glue, 73.
Fuel, consumption of, 127.
heating value of coal, 129.
GALLO-TANNIC acid, 4.
Gelatine, action with various salts, 53.
coating for pills, 84.
contraction of, 83.
decolorisation by charcoal, 51.
for artificial ivory manufacture, 85.
leather manufacture, 86,
Gelatine for mounting photographs,
printers' rollers, 87.
residual products from, 89.
use of, in photography, 82.
value as food, 81.
French and British, comparison of.
Glue, acidity of, 117.
adhesiveness of, 46.
loss of, by heating, 45.
ageing of, 47.
colour of, 47, 113.
effect of temperature and drying, 33.
estimation of, 113.
viscosity of, 45.
foam test for, 121.
for belts, 77.
leather goods, 75.
paper bags, 78.
foreign matter in, 117.
formation of, 11.
jelly, capacity for drying, 116.
melting point of, 116.
joints, holding power of, 140.
liquors, bleaching, 29.
moisture in, 112.
Russian liquid, 71,
Glue, Scotch, 40.
shot jelly, test for, 115.
shrinkage of, 113.
slow drying, 47.
sorting, for market, 56.
Rideau's method, 120.
uses of, 80.
viscosity of, 117, 139.
water absorbing, power of, 115.
white or Russian, 73.
yield of, 24.
Glues, liquid, 69.
for printing purposes, 70.
moisture proof, 71.
various, 74, 75.
Glutin, composition of, 118.
properties of, 3.
Gregory, on glue, 11.
HEATING glue, loss of tenacity due
value of coals, 128, 145.
Hides for gelatine manufacture, 48.
History of glue, 1.
Holding power of glue joints, 140.
Hot wood, glueing, 47.
Howard's vacuum pan, 25.
Hydraulic glue cutter, 31.
Hydrochloric acid, 48.
INDIAN ink, 86.
Isinglass, 48, 57.
composition, of, 60.
cutting of, 58.
Hudson's Bay, 57.
kinds of, 56.
uses of, 59.
Ivory, artificial, 85.
glue for, 74.
JEFFREY'S marine glue, 72.
Jeweller's cement, 76.
Joints, holding power of glue, 140.
KeldjahFs process for nitrogen, 110.
LABEL varnish, 79.
cement for, 76.
uses of, 106.
Lepowitz's method of glue testing,
Library, glue paste for, 77.
Liebig on gelatine, 81.
Lighting of factories, 6.
Liming of stock, 38.
Liquid glues, 69.
Liquors, tarry and ammoniacal, 67.
MAGNESIA mixture, 123.
Manures, degelatinised bone, 125.
estimation of, 125.
valuation of, 130.
Marine glues, 72.
Marrow bones, 64.
fat, composition of, 65.
manufacture of toilet soaps, 64.
Materials, raw, 36.
Meal, adulteration of, 92.
Meal, coarse bone, 19.
Measurement conversion tables, 148.
Mechanical cleanser, 19.
Metric system, 147.
Milling animal charcoal, 67.
Moisture in degelatinised bones, 124.
in glue, 114.
Moisture-proof glues, 71.
Molybdate of ammonium, 122.
Mont-jus, 16, 17.
Mulder, on gelatine, 37.
NAPHTHA in refined fat, 112.
Nitrate of soda, 98.
Nitrogen as a fertilizer, 89.
determination of, in degelatinised
raw bones, 110.
in fish residues, 90.
manures, 100, 126.
Oat manure, 102.
Onion manure, 102.
PERUVIAN guano, substitute for, 97.
Phosphate, Algerian, 100.
of lime as fertilizer, 89.
recovery of, 103.
Photography, use of gelatine in, 82.
Pills, gelatine coated, 84.
Portable glue, 73.
Potato manure, 100.
Printers' rollers, manufacture of, 87.
Public Health Act, in relation to
RAILWAY accommodation, 6.
Raw and finished products, valuation
Refined fat, 111.
Residual products from glue and
Rideau on glue testing, 120.
Rivers Pollution Act, 61.
Russian isinglass, 57, 59.
liquid glue, 73.
SCHNEIBLE cutting machine, 30.
Scotch glue, 40.
Seaweed gelatine, 52.
Shrinkage of glue, 113.
Shot jelly test for glue, 115.
Site, selection of, for factory, 5.
preservation of, 56.
Skin glue, 36.
raw materials for, 37.
Skins, nature of, 36.
preparation of, 38.
Slag, basic, 98.
Smith, Watson, on gelatine, 57.
Solvents for fats, 14.
Sorting glue for market, 56.
Soxhlet's extraction apparatus, 109.
Specifications for glue, 133 et seq.
Standard solutions, 143.
Steeping pits, 39.
Strohmeyer on water softening, 7.
Sugar cane manure, 104.
Sulphuric acid, 96.
Sulphurous acid, 29.
Superphosphates as fertiliser, 97.
estimation of insoluble phosphates
soluble phosphates in, 125.
TABLE jelly, 82.
Tanners' wastes, 130.
Tannic acid, 38.
action of, on glutin, 4.
Tannin titration, Bisler-Beaumat
Testing glue and gelatine, 138.
Thermometric tables, 146.
Toilet soap, 64.
Treatment of effluents, 6,
of marrow bones, 64.
Tungstic glue, 73.
VACUUM pan, 26.
Valuation of raw and finished
Value of glue, estimation of, 113.
Vanduara Silk Company, 87.
Viscosity of glue, 117.
WASHING bones, 49.
Waste products, treatment of, 61.
Water softening, 7.
Water- white gelatine, 52.
White glue, 73.
Weedenbusch method of testing glue,
YARYAN evaporator, 26 et seq.
ZINC sulphate, use of, to prevent
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